Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

Pattern transfer of large-scale thin membranes with controllable self-delamination interface for integrated functional systems

Pattern transfer of large-scale thin membranes with controllable self-delamination interface for... ARTICLE https://doi.org/10.1038/s41467-021-27208-5 OPEN Pattern transfer of large-scale thin membranes with controllable self-delamination interface for integrated functional systems 1 2 2 1,3,4 Jun Kyu Park , Yue Zhang , Baoxing Xu & Seok Kim Direct transfer of pre-patterned device-grade nano-to-microscale materials highly benefits many existing and potential, high performance, heterogeneously integrated functional sys- tems over conventional lithography-based microfabrication. We present, in combined theory and experiment, a self-delamination-driven pattern transfer of a single crystalline silicon thin membrane via well-controlled interfacial design in liquid media. This pattern transfer allows the usage of an intermediate or mediator substrate where both front and back sides of a thin membrane are capable of being integrated with standard lithographical processing, thereby achieving deterministic assembly of the thin membrane into a multi-functional system. Implementations of these capabilities are demonstrated in broad variety of applications ranging from electronics to microelectromechanical systems, wetting and filtration, and metamaterials. 1 2 Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA. Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, VA 22903, USA. Institute for Convergence Research and Education in Advanced Technology, Yonsei University, Seoul 03722, South Korea. Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, South Korea. email: seok.kim@postech.ac.kr NATURE COMMUNICATIONS | (2021) 12:6882 | https://doi.org/10.1038/s41467-021-27208-5 | www.nature.com/naturecommunications 1 1234567890():,; ARTICLE NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-27208-5 attern transfer on a substrate is essential for the integration onto a final target substrate for functional system assembly, as of nano-to-microscale materials into functional structures depeicted in Fig. 1, which has not been shown elsewhere to our Pand devices for a wide scope of applications. For example, knowledge. The theoretical model is established to understand the 1–3 lithographical pattern transfer (e.g. photolithography , e-beam transfer mechanism based on self-delamination in the liquid 4–6 7–9 lithography , imprinting lithography , etc.) that forms a media and provides a quantitative guide to experimental photoresist pattern on a substrate has been ubiquitously utilized demonstrations in great agreement. It is worthwhile to note that in top-down monolithic microfabrication together with successive the theoretical model certainly ensures the versatility and process steps (e.g., etching and deposition). However, it suffers robustness of this method to be readily extended for other from the process specific drawbacks, such as the requirement of a membrane materials while Si membranes are primarily utilized in flat substrate and the limited material compatibility. Alternatively, this work. The membrane–substrate adhesion is controllable 10–15 direct pattern transfer via transfer printing and contact upon material selection, and thus the adhesion can be high 16–20 transfer is relatively free from those challenges since it enough to allow a lithographical process on a membrane but generates a pattern on a target substrate by conveying formerly weak enough to retrieve it from a substrate using an elastomer patterned materials that are produced on a separate mother surface. This ability provides an opportunity to build an ideal substrate. To date, these methods to transfer patterned materials patterned Si platelet array which can be deterministically on one substrate to another have been done by direct contact with assembled into function structures or devices on a target substrate 17–20 a target substrate or by a polymeric mediator that is often using transfer printing. In addition, the reported pattern transfer 16 10–13 either a spin-coated layer or a reversible dry adhesive .In method makes complex 3D Si structures possible via one-step many cases, patterned materials formed on a mother substrate transfer since a patterned Si membrane can be transferred on and after undercutting a underneath sacrificial layer are transferred to adapted for a structured target substrate due to the low flexural a target substrate by either way. In the case of transfer printing, rigidity of the membrane. As opposed to other existing direct patterned materials together with a polymeric mediator are peeled pattern transfer methods, this method enables flip and transfer of off from a mother substrate and placed onto a target substrate. a patterned membrane which grants the choice of whether an Then the removal of the polymeric mediator finishes the transfer initially patterned membrane surface faces up or down after of patterned materials to the target substrate. Although, this type transfer. This capability allows for the multiple lithographical of direct pattern transfer has been a powerful protocol to deter- processes on both front and back sides of a thin large area Si ministically assemble nano-to-microscale materials onto target membrane as shown in Fig. 1. Here, we introduce the typical substrates, the entire pattern size of a transferred material has procedure of the reported pattern transfer method and theoreti- been limited, particularly for device-grade crystalline materials cally address how interfacial force between contacting surfaces (e.g. Si, GaAs, GaN, etc.) which are highly rigid and brittle. A thin changes to allow for the pattern transfer involving thin memrance large area brittle material is commonly prone to fracture during self-delamination in different environments. Next, we demon- transfer due to strain mismatch with a target substrate or poly- strate the versatility of this method with the microassembly of 21–24 meric mediator . Thus, direct pattern transfer of a large area both single-side and double-side patterned Si platelets. Moreover, device-grade material piece without physical damage is a sig- we show the hybrid microassembly of a light emitting diode nificant challenge, which would otherwise enable more diverse (LED) circuit relying on transfer of a metal patterned Si mem- cost-effective functional integrated structures and devices. brane and surface tension-driven self-alignment. Finally, the In this work, we report a pattern transfer method that is simple and economic fabrication of challenging re-entrant enabled by self-delamination of a thin membrane from a sub- structures is exhibited. Particularly, the fabricated re-entrant strate via controlled interfacial force in liquid environments structures show omniphobicitiy and even advanced functional- particularly to directly transfer a thin and large area patterned ities such as directional omniphobicity and selective permeability single crystalline silicon (Si) membrane onto nearly any type of for filtration applications. In addition to using Si, we also used target substrate. Remarkably, the Si membrane can be litho- polyimide (PI) and designed an auxetic patterned PI membrane graphically processed on mediator substrates several times and with negative Poisson ratio to present the concept of stretch- then, in a well controlled self-delamination manner, transferred induced tunable filtration. Material 2 Si membrane (Device layer) Acetone Material 1 ② SiO ① Transfer & Remove SiO Mother 2 Mediator substrate Lithographical Self-delaminate substrate (Silanized glass) HF process (SOI) Self-delaminate Material 3 Acetone Acetone Flip & Self-delaminate Transfer & Lithographical process Fig. 1 Self-delamination based pattern transfer and its implementation into classic lithographical process of functional devices. See Supplementary Fig. 1 for the details of other variants. It starts with the initial patterning of a Si membrane on a mother substrate before transferring to a mediator substrate for subsequent processes. The processed Si memberane is flipped and transferred to another mediator substrate for further processing on the back side. Finally, the patterned Si membrane is self-delaminated from the mediator substrate and transferred to a target substrate for use. 2 NATURE COMMUNICATIONS | (2021) 12:6882 | https://doi.org/10.1038/s41467-021-27208-5 | www.nature.com/naturecommunications NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-27208-5 ARTICLE =0 =0.2 =0.4 =0.6 <0 -13 Self-delaminaon -26 0 45 90 135 180 (degree) Experiment Si/Glass/Water ( =0) Self-delamination Si/Silanized Glass/Water ( =0) Si/Glass/Acetone ( =0) Si/Silanized Glass/Acetone Theory ( =0) Si/Si/Water ( =0) No self-delamination Si/Si/Acetone ( = 0, 0.2, 0.4, 0.7) -1 Fig. 2 Theoretical model of thin film self-delamination from a substrate in liquid. a Schematic illustration of mechanics model of peeling a thin film with arrays of microscale holes and width b from a substrate in liquid by a peeling force F at a 90° degree peeling angle. b Theoretical calculations of peeling force per unit width F=b as a function of the thin film surface wettability θ for films with different ρ (total holes area over total film area), where tl G ¼ 29:4 mN/m, θ ¼ 20 , and γ ¼ 24 mN/m. c Theoretical phase diagram on the successful conditions of thin film self-delamination, which are ts sl experimentally confirmed on a wide variety of system materials for substrate, thin film, and liquid. Results and discussion membrane is modeled as a thin film with width of b peeled off from The reported pattern transfer method introduced in Fig. 1 is a substrate by a peeling force F at a 90° peeling angle in a liquid implemented in two different modes and the details are sum- environment (Fig. 2a). For a quasi-static peeling process, with a marized in Supplementary Fig. 1. The procedure starts with the small peeling distance 4l in the direction of peeling force F,the initial patterning of a Si device layer of a silicon-on-insulator energy balance between the work done by peeling force 4W and (SOI) mother substrate with HF compatible material (material 1) the change of associated surface energy 4E at the steady-state surface and forming etch holes on it. Removal of SiO layer in a HF bath transfer leads to W ¼4E ¼ F4l. When a porous film with surface porosity ρ delaminates from a substrate in liquid, the change of makes the Si device layer stick on the mother substrate. Sub- effective contact area is 4lð1  ρÞb. Therefore, the change of surface merging it in an acetone bath enables the controlled interfacial 25,26 energy is 4E ¼ G  γ ðcosθ þ cosθ Þ 4lð1  ρÞb ; force-driven self-delamination of the Si device layer, i.e., Si surface ts l tl sl where γ is liquid surface tension, θ and θ are the contact angle membrane, from the mother substrate. This is one example of the l tl sl of liquid on thin film and substrate, respectively, and reflects their theoretically designed self-delamination of a membrane from a surface wettability. G is the interfacial adhesion energy between substrate in a liquid environment which is the key to the fol- ts thin film and substrate in a dry air condition, and G ¼ γ þ γ lowing patten transfer routes. For application demonstration of ts t s γ where γ and γ arethe surfacetension of thin film and sub- the self-delaminated Si membrane, it is transferred to other ts t s strate, respectively, and γ is the interfacial tension between thin ts substrate in one of two following modes. In Mode 1, the Si film and substrate. With W ¼4E ¼ F4l, the peeling force membrane transferred on a target substrate is etched into small surface per unit width is now written as platelets using material 1 etch mask and the platelets are ready for use, which is labeled (1) in Supplementary Fig. 1. A variant of F=b ¼ðG  γ cosθ þ cosθ Þ 1  ρ : ð1Þ ts tl sl Mode 1 where the Si membrane transferred on a mediator sub- strate is lithographically processed with material 2 is labeled (2) in When the required peeling force per unit width F=b ≤ 0, Eq. Supplementary Fig. 1. The processed Si membrane may further be (1) shows that a film is self-delaminated from a substrate in transferred on the second mediator substrate after flip to process liquid, and at F=b>0, applying an external force F becomes the back side surface with material 3. The Si membrane is finally necessary for achieving the delamination. Figure 2b represents the transferred on a target substrate for use. In Mode 2, the initially plot of the required F=b along with the porosity and wettability of patterned Si membrane is transferred on a target substrate for use thin film when G ¼ 29:4 mN/m, θ ¼ 20 , and γ ¼ 24 mN/m. ts sl without further process. Similarly, Supplementary Figs. 2a, Sb show the effect of wett- The mechanics of the reported pattern transfer method involves ability of substrate and interfacial adhesion energy between thin the deterministic self-delamination of a Si membrane from a film and substrate on the required F=b, respectively. The required mother or mediator substrate via controlled interfacial force. A Si peeling strength F=b increases with the incressing of interfacial NATURE COMMUNICATIONS | (2021) 12:6882 | https://doi.org/10.1038/s41467-021-27208-5 | www.nature.com/naturecommunications 3 / (mN/m) ARTICLE NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-27208-5 adhesion energy G and F=b becomes larger than 0 for all the ts Si membrane Au pattern Au/Si platelets porosity of film when G is beyond a critical value such as the ts large van der Waals interaction force . In this scenario, applying an external mechanical peeling force is required to assist the delamination at the interface between film and substrate. As indicated in Eq. (1), a thin film is easily peeled off from a substrate in a liquid environment when the wettability is high, the film–substrate interfacial adhesion energy is low, or the porosity of a film is large. To prove this, various pairs of substrate and liquid for a Si membrane are experimentally investigated and the 5 mm 5 mm Target favorable pairs for peeling are found. As shown in Fig. 2c, the substrate theoretical diagram calculated using Eq. (1) with ρ ¼ 0 agrees well with the experiment results. In the theoretical diagram, the purple curve represents the theoretical prediction on critical condition of thin film self-delamination. The symbols represent the experimental results, where the open symbol denotes no self- delamination and the solid symbol denotes self-delamination. The colors of symbols define material types of film/substrate/ liquid. Supplementary Table 1 provides the values of parameters (G, contact angle, surface tension) which are calculated using the 28–30 harmonic mean equation . Guided by the theoretical analysis 100 μm 5 mm in Eq. (1) and the related experimental results, an acetone med- ium is selected to effectively peel a Si membrane from a Si mother Stamp substrate and a silanized glass substrate is chosen as an mediator substrate in this work. In addition, the theoretically calculated effect of porosity on F=b is experimentally proven. Si membranes with different porosity of 0.04, 0.2, 0.4, and 0.7 are prepared as shown in Supplementary Fig. 3 and the experimental results also Pick-up qualitatively shows that a higher porosity Si membrane is more favorable for peeling off from a Si substrate in an acetone med- ium. The computational modeling of the self-delamination of a film on substrates with a broad variety of materials is similar to 100 μm 100 μm that of peeling a film from substrates under an applied Mediator substrate mechanical force where molecular dynamics (MD) simulations Au/Si Si Au/Si (silanized glass) platelet can be employed . Substrate platelet Once the self-delaminated patterned thin membrane is obtained, it can be readily implemented into other processes d (outlined in Supplementary Fig. 1) for fabricating integrated functional systems. Figure 3 summarizes how Mode I (1) of the reported pattern transfer enables the production of microscale device-grade Au-coated Si platelets on a target substrate. The method begins with preparing a Si membrane with the initial pattern of deposited material (e.g. metals) on a SOI substrate (Supplementary Fig. 4a). After the complete removal of SiO sacrificial layer, the Si membrane is delaminated from a mother 100 μm SOI substrate by soaking in the acetone bath (Supplementary Fig. 4b). The Si membrane floating on liquid is transferred to a Fig. 3 Au/Si platelets on a target substrate after Mode I (1) procedure in glass target substrate with liquid (Fig. 3a left). Then drying of the Supplementary Fig. 1 and their application to microassembly via transfer underlying liquid forms tight contact between two surfaces via printing. a A schematic illustration of a Au patterned Si membrane in a rose surface tension-induced pressure 4P ¼ γ ðcosθ þ cosθ Þ=h, l tl sl mosaic shape on a target substrate before and after Si etching. b Optical where h is the distance between the Si membrane and the glass and magnified SEM images of the Au/Si platelet array. Au areas are yellow 31,32 substrate . After that, the Si membrane is dissected into an colored. c Cartoons of the microassembly of Au/Si platelets via transfer array of microscale Au/Si platelets by reactive ion etch (RIE) with printing. d A colored SEM image of assembled Au/Si platelets with the Au pattern as a hard mask (Fig. 3a, b). Consequently, a pack incremental rotations after thermal joining. Au areas are yellow colored. of aligned Au/Si platelets in various configurations regardless of the target substrate material (e.g. glass, PDMS, etc.) can be pro- duced. A rose mosaic shape pattern on a glass substrate is shown to hold Au/Si platelets but also to ensure the reliable retrieval of in Fig. 3b. Additional patterns of Au/Si platelets on glass as well as them by a polymeric stamp. Figure 3c shows this trait with car- curved PDMS substrates are shown in Supplementary Fig. 5. toons that retrieved Au/Si platelets are easily stacked without Apparently, the soft PDMS surface with a Au/Si platelet array is failure. Furthermore, these stacked Si platelets are thermally highly bendable, which envisions its potential applications toward joined by employing the eutectic bonding between Si and Au flexible electronics. surfaces to form a robust microscale structure with a unique 3D 33,34 Remarkably, the glass target substrate where a Si membrane is shape as shown in Fig. 3d . transferred and patterned may become a perfect mediator sub- Mode I (2) of the reported pattern transfer allows a Si mem- strate if it is coated with an anti-stick monolayer or silanized. brane to be attached to and detached from a mediator substrate Here, the mediator substrate is with moderate adhesion not only several times in liquid, which provides a powerful route to 4 NATURE COMMUNICATIONS | (2021) 12:6882 | https://doi.org/10.1038/s41467-021-27208-5 | www.nature.com/naturecommunications NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-27208-5 ARTICLE multiple microfabrication processes of a Si membrane as depicted electric circuit is connected and then, serially positioned RGB in the second row of Supplementary Fig. 1. Since the mediator LEDs are turned on with an external power supply. In addition, substrate needs no sacrificial layer, there is no process constraint Fig. 5c, d show that the interaction between a Si membrane and a caused by using a sacrificial layer. For example, making a Si curved target substrate transforms a 2D patterned Si membrane membrane directly from an SOI wafer does not allow depositing into a 3D structure due to the low flexural rigidity of the Si any materials incompatible with HF since it should finally be used membrane. For this purpose, a Si membrane should be thin and to remove a SiO sacrificial layer at the end of conventional Si patterned into a shape that ensures the geometric flexibility 12,18,33–35 membrane preparation protocols . In addition, via Mode (Supplementary Fig. 10a). After a Si membrane is transferred I (2), a Si membrane is easily flipped in liquid and stay upside- onto a 3D dome-shape PDMS target substrate, the strong contact down on a mediator substrate. Therefore, both front and back in between is made during the evaporation of underlying liquid. sides of the Si membrane can be processed and patterned to have The optical images and finite-element analysis (FEA) plots of 3D dual functionalities that do not interrupt each other. This ability assembled Si membranes in saddle and dome shapes depending is exceptional since conventional Si membrane preparation pro- on their initial pattern designs are shown in Figs. 5d and S10b. tocols require sophisticated patterning steps on only one side to Mode II of the reported pattern transfer also varies to allow a have multi-functions, which often sacrifices other structural pre-patterned membrane to be used on a target substrate for 12,18,33–35 performance . other novel functionalities. Figure 6 captures representative To demonstrate this exceptional ability, a double-side patterned examples of omniphobic surfaces which are built using the pat- sunflower-like Si platelet is fabricated as shown in Fig. 4a. On the tern transfer Mode II. While omniphobic surfaces have received front side, black Si and thin gold surfaces are patterned to mimic a much attention due to their repellency toward liquids with 39–43 sunflower using structural coloration and material color. On the extremely low surface tensions , forming them requires back side, a NdFeB hard magnet material is deposited and magne- complex fabrication steps since they are commonly with re- tized in one direction. The detailed process steps are available in entrant structural designs. The pattern transfer of this work may Supplementary Fig. 7. Then the double-side patterned Si platelet is provide the cost effective route to these complex re-entrant retrievedand assembledontop of a flexible PDMS pillar, which structures. Figure 6a shows a pre-patterned Si membrane that is finishes the fabrication of a sunflower-like structure with dual transferred on a continuous uncrosslinked SU8 negative photo- functionalities as shown in Fig. 4a. Due to the structural coloration, resist layer. Using an additional photomask combined with the the center portion of the Si platelet is deep black. On the other hand, transferred Si membrane enabling the self-aligned photo- the assembled structure is actuated by an external magnetic field lithography, only SU8 under rectangular openings is cured and a thanks to the strong magnetization in a NdFeB layer on the back hexagonal lattice re-entrant structure is simply constructed. This side of the Si platelet. Implementing both the structural coloration by structure is called Si/SU8 hereafter. Even simpler approach black Si and the magnetic motion by a NdFeB layer on only one side involves just a hexagonal patterned Si membrane transferred on a would be impossible as a NdFeB magnetic layer on top of black Si PDMS slab with a punched hole as depicted in Fig. 6b. The figure would diminish the structural coloration. Exceptionally, the reported shows the transfer illustrations and the image of the hexagonal Mode I (2) route to double-side processing of a Si platelet allows two patterned Si membrane on the punched PDMS slab. This struc- incompatible functionalities to reside in a single Si platelet without ture is called Si/PDMS hereafter. On these two re-entrant struc- compromising any performance. tures, even liquid with a low energy can build up an upward The tilting angle of the sunflower-like structure under an surface tension to be suspended as shown in Fig. 6c. To confirm external magnetic field B can be predicted by equating the their omniphobic characteristics, four liquids with different sur- magnetic torque V MBsin π=2  θ and the elastic restoring face tensions (γ) including water (γ = 72.8 mN/m), ethylene torque K θ, where V is the volume of a magnetic material, M is glycol (γ = 48.0 mN/m), acetone (γ = 24 mN/m), and hexane eq m a magnetization strength, K is the equivalent torsion spring (γ = 18 mN/m) are used. In addition, three different solid fraction eq hexagonal pattern designs of Si membranes and nanostructured constant, and θ is the tilting angle . As depicted in Fig. 4b, counterparts are prepared for Si/SU8 and Si/PDMS surfaces. The experimentally measured tilting angles match well with analytical geometric designs of the patterned Si membranes are in Supple- computed tilting angles, which confirms the intact magnetic mentary Fig. 11. As shown in Fig. 6d, e, all surfaces are able to motion of the Si platelet. A series of optical images of the repel relatively high surface tension liquid such as water and sunflower-like structure under different magnetic field strength ethylene glycol. However, only Si/PDMS surfaces can reliably (0, 0.55, 0.7, 0.8 T) is available in Supplementary Fig. 8. Finally, suspend liquids with very low surface tensions such as acetone Fig. 4c shows the motion of the sunflower-like structure that tilts and hexane. For Si/SU8 surfaces with the solid fraction of 0.18, upon an external magnetic field mimicking sunflower motion that those low surface tension liquids smear into the structures and tracks the sun during the daytime. forms nearly 0° contact angle showing the Wenzel state wetting as Alternatively, a pre-patterned Si membrane can be directly shown in Fig. 6e. The trend between apparent contact angle (θ ) transferred onto a target substrate where it is utilized as the final and solid fraction (f ) is theoretically predicted using the equation form, which is Mode II as depicted in the third row of Supple- of cosθ ¼ f cosθ þ 1  1 when droplets are in suspended mentary Fig. 1. Figure 5a shows a Au patterned Si membrane state , where θ is the intrinsic contact angle of water (θ = transferred on a target substrate with a disconnected red-green- 110°), ethylene glycol (θ = 85°), acetone (θ = 25°), or hexane blue (RGB) LED circuit. The optical images of a Si membrane as Y Y (θ = 5°) on a silanized either Si or SU8 surface. The solid frac- well as a target substrate are in Supplementary Fig. 9. Once a Si tion (f) of assembled surfaces are available in Supplementary membrane is delaminated from a mother substrate, the Si Fig. 12. As shown in Fig. 6d, measured apparent contact angle membrane is flipped inside a liquid medium and transferred onto values match well with theoretically calculated ones, which a target substrate. For the precision assembly, the target substrate demonstrates the deterministic omniphobic characteristics of the has a hydrophilic pattern on a square region to induce the surface re-entrant surfaces which are simply fabricated using the reported tension-driven self-alignment of the Si membrane during the pattern transfer. evaporation of underlying deionized (DI) water as shown in 36–38 When patterned Si membranes are covered with black Si Figs. 5b and S9b . The actual self-alignment procedure is nanostructures, the roughness ratio (r ) is increased to 2.8 from 1 captured in Supplementary Movie 1. After the assembly, the NATURE COMMUNICATIONS | (2021) 12:6882 | https://doi.org/10.1038/s41467-021-27208-5 | www.nature.com/naturecommunications 5 ARTICLE NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-27208-5 Fig. 4 A double-side patterned Si platelet with dual functions of structural coloration and magnetic motion after Mode I (2) procedure in Supplementary Fig. 1. a A schematic illustration of the composition of a double-side patterned Si platelet. One side is formed by black silicon nanostructures and gold patterns representing a sunflower and the other side is loaded with a NdFeB magnet alloy. The Si platelet transferred on a PDMS pillar is actuated by an external magnetic field after magnetization. b A graph showing tilting angle of the fabricated structure as a function of magnetic field strength. c Optical images for the tilting motion of the sunflower-like structure upon an external magnetic field. a Au patterned Si membrane RGB Micro LEDs 5 mm 5 mm Self-aligned transfer on hydrophilic region 1 cm Target substrate 5 mm 1 cm c d Si membrane PDMS dome Transfer on dome 4 mm 4 mm Fig. 5 An LED circuit and single crystalline Si 3D mesostructures after Mode II procedure in Supplementary Fig. 1. a A schematic illustration of the assembly process including flipping and transferring of a Au patterned Si membrane. A target substrate has a square hydrophilic region to enable the surface tension-driven self-alignment assembly. b A series of optical images of the self-alignment during underlying liquid drying and an optical image of assembled RGB LED circuit. c A schematic illustration of the process to build 3D Si mesostructures. Patterned Si membranes are transferred on structured PDMS domes. d Optical images of the resulted 3D Si mesostructures. 6 NATURE COMMUNICATIONS | (2021) 12:6882 | https://doi.org/10.1038/s41467-021-27208-5 | www.nature.com/naturecommunications NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-27208-5 ARTICLE Fig. 6 Patterned Si membranes demonstrating omniphobicity. a A schematic step to fabricate a re-entrant surface composed of a pre-patterned Si membrane on an SU8 layer involving the self-aligned photolithography. The right SEM image with brown colored SU8 structures presents the high structural integrity of the resultant Si/SU8 surface. b A schematic step to form a hexagonal patterned Si membrane on a punched PDMS. The right optical image depicts the resultant Si/PDMS surface. c Illustrations showing the upward surface tension of a low energy liquid droplet placed on Si/SU8 (upper) and Si/PDMS (lower) surfaces enabling omniphobicity. d A graph showing apparent contact angle of diverse liquids as a function of different solid fraction of Si/SU8 and Si/PDMS surfaces. e A graph showing apparent contact angle of diverse liquids as a function of their surface tension on Si/SU8 (red) and Si/PDMS (black) surfaces with f = 0.18 and f = 0.13, respectively. f A graph showing apparent contact angle of diverse liquids as a function of solid fraction of Si/PDMS surfaces. Si surfaces are either smooth (r =1, solid symbol) or nanostructured (r =2.8, hollow symbol). f f and it makes the assembled Si/PDMS surfaces superhydrophobic the auxetic lattice PI membrane increases because its Poisson’s as shown in Fig. 6f. The roughness ratio of the nanostructured ratio is negative. The ability to suspend a liquid droplet is surface is measured using an AFM technique and is found in inversely proportional to the lattice dimension (L ). With the Supplementary Fig. 13. However, the roughness ratio acts dif- negative Poisson’s ratio, the mechanical stretch-induced switch- ferently for liquids with lower surface tension (θ < 90°), and able omniphobicity is achieved in the auxetic lattice PI membrane causes the reduced omniphobicity. This difference is explained as opposed to conventional grid pattern surfaces. To show this capability, a droplet of vegetable oil is placed and suspended on using the equation of cosθ ¼fr cosθ þ 1  1 that is used f Y both hexagonal and auxetic lattice PI membranes. Then the for a solid surface with a roughness . Apparently, the negative membranes are uniaxially stretched and only the oil droplet on cosθ term for a lower surface tension (θ < 90°) liquid decreases Y Y the auxetic lattice PI membrane penetrates it. The detailed cosθ . Figure 6f does not include data for hexane which is chal- experimental results are captured in Supplementary Movie 2. lenging for the nanostructured Si/PDMS surface to reliably Remarkably, the assembled Si/PDMS surface shown in Fig. 6 suspend. demonstrates the switchable wettability macroscopically Furthermore, inspired by the simple Si/PDMS surface fabri- depending on the configuration of the assembly although its cation step presented in Fig. 6, a mechanical metamaterial made microscopic wettability is still omniphobic. When a Si membrane of PI is designed to show the stretch-induced switchable wett- is facing upward as depicted in left column of Fig. 7b, the mac- ability. Here, auxetic (metamaterial sample) and hexagonal roscopic wettability is dictated by the property of PDMS (control sample) patterned PI membranes are transferred and (hydrophobic and oleophilic) as a liquid droplet meets with the bonded to a punched PDMS slab. The fabrication steps for PI underneath punched PDMS sidewall. Here, a 500 μm-thick PI membranes are available in Supplementary Fig. 14. When the sheet is added to ensure the structural rigidity of the assembled hexagonal lattice PI membrane is uniaxially stretched, the lattice surface. Therefore, vegetable oil (γ = 32 mN/m) pass through the dimension (L ) normal to the stretching direction decreases assembled surface. On the other hand, when the Si membrane is because of its positive Poisson’s ratio (Fig. 7a). However, that of NATURE COMMUNICATIONS | (2021) 12:6882 | https://doi.org/10.1038/s41467-021-27208-5 | www.nature.com/naturecommunications 7 ARTICLE NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-27208-5 Stretch-induced switchable omniphobicity 0 % uniaxial strain 40 % uniaxial strain Hexagonal lace 100 μm 100 μm 3 mm Auxec lace 100 μm 100 μm b Directional omniphobicity Veg Oil Veg Oil Si membrane PI backbone PDMS PDMS PI backbone Si membrane Oleophilic & Omniphobic 1 cm 1 cm Hydrohpobic (c) Selective chloroform/water filtration Water Chloroform Chloroform Water Si membrane Si membrane PDMS PDMS PI backbone PI backbone Oleophilic & Oleophilic & Hydropohbic Hydropohbic 1 cm 1 cm Fig. 7 PI membranes showing stretch-induced switchable omniphobicity, and hexagonal patterned Si membranes demonstrating directional omniphobicity and selective filtration. a Illustrations and images of PI membranes with auxetic lattice design for novel stretch-induced switchable wettability and with counterpart hexagonal lattice design. b An assembled oleophilic Si/PDMS/PI surface where vegetable oil passes (left) and an omniphobic PI/PDMS/Si surface where vegetable oil does not pass (right). c Selective filtration of chloroform/water mixture using the assembled oleophilic yet hydrophobic Si/PDMS/PI surface where chloroform passes, yet water is trapped. facing down as depicted in right column of Fig. 7b, the assembled is controlled by the material underneath the patterned Si mem- surface becomes purely omniphobic as liquid does not meet any brane, other variations are also possible by changing the under- other surfaces under the Si membrane. Consequently, vegetable neath material. Supplementary Fig. 15 and Supplementary oil does not pass through the assembled surface. More demon- Movie 5 depict one of the variations where the assembled surface strative experimental results are available in Supplementary is omniphilic using a water and oil permeable material, such as Movie 3. TexWipe under the Si membrane. While the assembled Si/ The straightforward application of these unique capabilities of PDMS surface show promising potentials towards directional the assembled Si/PDMS/PI surface should be to separate water wettability and resultant filtration applications, its functionalities from low surface tension liquids. As a part of example, the are from unique structural designs enabled by the simple pattern mixture between water (γ = 72.8 mN/m) and chloroform transfer methods presented in this work. (γ = 27 mN/m) is prepared and poured into the assembled sur- This work reports the unique capabilities of a thin membrane face where a Si membrane is facing upward as shown in Fig. 7c. pattern transfer method which relies on determinate control of Since the macroscopic wettability of the assembled surface is interfacial force between contacting surfaces in liquid environ- oleophilic and hydrophobic, chloroform passes through the ments and theoretical explanations to understand key parameters assembled surface and is collected in an underneath container determining optimal membrane-substrate–liquid combinations. while water is trapped on top of the assembled surface. Supple- Particularly, a pre-patterned device-grade single crystalline Si mentary Movie 4 presents more details of the experimental membrane is easily transferred to nearly any type of substrates results. Since the macroscale wettability of the assembled surface encompassing a silanized glass mediator substrate for use or 8 NATURE COMMUNICATIONS | (2021) 12:6882 | https://doi.org/10.1038/s41467-021-27208-5 | www.nature.com/naturecommunications NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-27208-5 ARTICLE further microfabrication processes. Upon these unique cap- the Si membrane with Au/Cr pattern (Supplementary Fig. 9a) is flipped inside acetone bath and moved to DI water bath. After that, the Si membrane transferred abilities, the versatility of this approach is summarized by onto the hydrophilic region with DI water. DI water is let dried for 24 h to ensure demonstrating the microassembly of single- and double-side tight contact is made between the Si membrane and the target substrate. RGB LEDs patterned Si membranes, the hybrid assembly of RGB LED circuit (SMD 0603, Dialight) are connected to the assembled circuit using silver epoxy especially assisted with the surface tension-driven self-alignment. (8331S, MG chemicals). Finally, 10 V is applied to turn the LED lights on through soldered copper wire. Moreover, re-entrant shape patterned surfaces are straightfor- To build single crystalline Si 3D mesostructures, an SOI device layer (3 μm) is wardly and cost-effectively fabricated for surface directional patterned by using SF (20 sccm) and O (2 sccm) plasma with 150 W at 20 mTorr 6 2 omniphobicity and selective filtration purposes, which highlights for 6 min with photoresist as masking layer (Supplementary Fig. 10a). PDMS dome the potential of the reported approach towards diverse applica- structures are prepared by pouring 10:1 base to curing agent ratio PDMS precursor (Sylgard 184, Dow Chemical) on a mold. Then the Si membranes are transferred tions. Future opportunities include extending thin membrane onto the cured PDMS dome structures with underlying liquids. Here the outer ring material choices possibly using guidance from further theoretical in Supplementary Fig. 10a is used to manually align an Si membrane and a PDMS models and enabling more precision assembly processes dome structure and is removed after contact. employing advanced equipment and tooling. Fabrication of omniphobic Si/SU8 surfaces. Negative photoresist (SU8-50, Microchem) is spun on a Si substrate with 3000 rpm and soft baked at 65 °C for Methods 5 min and at 95 °C for 15 min. This yielded 40 μm-thick soft baked SU8 layer on a Fabrication and transfer of Si membrane with Au pattern. Fabrication of a Si Si substrate. A separately prepared pre-patterned Si membrane is delaminated from membrane starts with rinsing an SOI wafer (3 μm-thick device layer and 1 μm- its mother substrate in acetone bath and transferred to IPA bath for selectivity. thick SiO sacrificial layer) with acetone, IPA, and DI water followed by drying Then it is transferred to the soft baked SU8 layer. Drying out the underlying IPA under a stream of nitrogen. Cr (5 nm)/Au (50 nm) is deposited using e-beam and subsequent heating on 65 °C for 5 min makes conformal contact between SU8 evaporation (FC-2000, Termescal) onto the device layer of SOI wafer and wet and the SI membrane. After that, 200 mJ/cm of UV light is selectively exposed to etched through a mask of photoresist (AZ5214, Microchem) as shown in Sup- rectangular openings, which defines supporting SU8 pillars connected to the Si plementary Fig. 3a. Then the Si device layer is patterned into a desired shape using substrate. The assembled substrate is hard baked at 65 °C for 1 min and 95 °C for SF (20 sccm) and O (2 sccm) plasma at 150 W, 20 mTorr for 6 min. After that, 6 2 5 min. Using SU8 developer (Microchem), SU8 is developed to define rectangular the sample is immersed in HF bath for 6–12 h to remove the SiO sacrificial layer. pillar. The resultant structure surface is modified by depositing silane (Tri- The patterned Si membrane is delaminated from the mother SOI substrate by chloro(1H,1H,2H,2H,-perfluorooctyl)silane, Sigma Aldrich). immersing in acetone bath as shown in Supplementary Fig. 4b. Then the floating Si membrane is scooped with acetone and transferred onto a target substrate. Drying of underlying liquid completes the pattern transfer of a Si membrane with Au Fabrication of hexagonal and auxetic lattice PI membranes. PMMA (PMMA pattern. A7, Microchem) is spun on a Si wafer at 3500 rpm for 40 s and baked at 180 °C for 3.5 min. Then PI (PI-2545, Dupont) is spun on the PMMA layer at 2000 rpm for 60 s and cured at 250 °C in a vacuum oven. This yields a 3 μm-thick PI layer with sufficient Patterning of Si membrane into Au/Si platelets and transfer printing of Au/Si thickness uniformity. Cr (5 nm)/Au (20 nm) is deposited by e-beam evaporation (FC- platelets. Once a Si membrane with Au pattern is transferred on a target substrate. 2000, Temescal) onto the PI layer and wet etched through a mask of photoresist The Si membrane is dissected into Au/Si platelets using SF (20 sccm) and O 6 2 (AZ5214, Microchem) as the PI layer to have hexagonal or auxetic designs (Supple- (2 sccm) plasma at 150 W, 20 mTorr for 6 min with the Au pattern as an etching mentary Fig. 14a). Using the Cr/Au layer as an etch mask, the PI and PMMA layers mask as shown in Supplementary Fig. 6. When the target substrate is a silanized are dry-etched using an O plasma at 20 sccm with 200 W at 50 mTorr for 10 min glass substrate, Au/Si platelets on it are easily picked up using a PDMS stamp. The (Supplementary Fig. 14b). Then the sample is immersed in acetone bath for 24 h to PDMS stamp is brought into contact with a Si platelet with preload and rapidly remove the PMMA sacrificial layer and release the PI membrane from the wafer. The retracted to pick up a Au/Si platelet. The Au/Si platelets are transferred to another PI membranes are transferred onto punched PDMS slabs to suspend hexagonal or target Si substrate with translation and angular alignment to build a stacked auxetic design parts (Supplementary Fig. 14c). Then the assembled surface is cut into a structure shown in Fig. 3d. After stacking, the Au/Si platelets are thermally joined stretchable shape (Supplementary Fig. 14d). in rapid thermal processing (RTP) furnace at 360 °C for 10 min. Data availability Fabrication of sunflower mimicking structure. A device layer of an SOI wafer All data used and generated in this study are available in Supporting Information. (10 μm-thick device layer and 1 μm-thick SiO sacrificial layer) is partially patterned with black Si nanostructures. To pattern black Si nanostructure, native oxide on Si surface is removed in HF bath for 1 min. Then thin oxide layer was grown by O Received: 10 August 2021; Accepted: 3 November 2021; plasma at 10 sccm, RF1 120 W, RF2 200 W at 50 mTorr for 5 min. The oxide layer is incompletely etched by CHF plasma at 12 sccm, 350 W at 50 mTorr for 2 min. Using the left oxide islands as an etching mask Si is slowly etched by Cl (40 sccm) and Ar (4 sccm) plasma RF1 250 W, RF2 300 W at 90 mTorr for 10 min to form sharp and dense nanostructures. Then the Si membrane is patterned by DRIE process such that a Si platelet array is mechanically supported by the Si membrane (Supplementary Fig. 7a). Then the Si membrane is delaminated and flipped from the mother substrate References inside the liquid medium, and transferred on a silanized glass substrate. On the glass 1. Bratton, D., Yang, D., Dai, J. & Ober, C. K. Recent progress in high resolution substrate, Cr (5 nm)/Au (50 nm) is patterned by a lift-off process with a photoresist lithography. Polym. Adv. Technol. 17,94–103 (2006). masking layer (SPR220, Microchem). Once the front side process is finished, the Si 2. Pimpin, A. & Srituravanich, W. Review on micro-and nanolithography membrane is delaminated again in acetone bath (Supplementary Fig. 7b) and trans- techniques and their applications. Eng. J. 16,37–56 (2012). ferred to a new silanized glass substrate for backside processing as depicted in Sup- 3. Wu, B. & Kumar, A. Extreme ultraviolet lithography: a review. J. Vac. Sci. plementary Fig. 7c. On the Si membrane, Ti (10 nm)/NdFeB (400 nm)/Ti (10 nm) are Technol. B 25, 1743–1761 (2007). sputter deposited. After the deposition, the NdFeB layer is magnetized under 1.9 T 4. Chen, Y. Nanofabrication by electron beam lithography and its applications: a magnetic field and delaminated from the glass substrate (Supplementary Fig. 7d). After review. Microelectron. Eng. 135,57–72 (2015). transfer to another new silanized glass substrate, a Si platelet is mechanically unteth- 5. Tseng, A. A., Chen, K., Chen, C. D. & Ma, K. J. Electron beam lithography in ered form the Si membrane and picked up by a PDMS pillar to be a sunflower nanoscale fabrication: recent development. IEEE Trans. Electron. Packag. mimicking structure (Supplementary Fig. 7e, S7f). Manuf. 26, 141–149 (2003). 6. Altissimo, M. E-beam lithography for micro-/nanofabrication. Biomicrofluidics 4, 026503 (2010). Fabrication of LED circuit and single crystalline Si 3D mesostructures.To 7. Kooy, N., Mohamed, K., Pin, L. T. & Guan, O. S. A review of roll-to-roll build a LED circuit, Cr (5 nm)/Au (20 nm) is deposited by e-beam evaporation nanoimprint lithography. Nanoscale Res. Lett. 9,1–13 (2014). (FC-2000, Temescal) on a SOI device layer (3 μm) and a Si wafer. Then the 8. Schift, H. Nanoimprint lithography: 2D or not 2D? A review. Appl. Phys. A deposited layers are wet etched through a mask of photoresist (AZ5214, Micro- 121, 415–435 (2015). chem) as shown in Supplementary Fig. 9. To fabricate a Si membrane, a gold- patterned SOI wafer device layer is etched by SF (20 sccm) and O (2 sccm) 9. Balla, T., Spearing, S. M. & Monk, A. An assessment of the process capabilities 6 2 plasma with 150 W at 20 mTorr for 6 min. To pattern a square hydrophilic region of nanoimprint lithography. J. Phys. D 41, 174001 (2008). on a target substrate, a mask of photoresist is patterned on the square area and 10. Carlson, A., Bowen, A. M., Huang, Y., Nuzzo, R. G. & Rogers, J. A. Transfer silane (Trichloro(1H,1H,2H,2H,-perfluorooctyl)silane, Sigma Aldrich) is selectively printing techniques for materials assembly and micro/nanodevice fabrication. deposited using the photoresist as a masking layer (Supplementary Fig. 9b). The Adv. Mater. 24, 5284–5318 (2012). target substrate is cleaned with acetone and IPA to remove the masking layer. Then NATURE COMMUNICATIONS | (2021) 12:6882 | https://doi.org/10.1038/s41467-021-27208-5 | www.nature.com/naturecommunications 9 ARTICLE NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-27208-5 11. Loo, Y. L., Willett, R. L., Baldwin, K. W. & Rogers, J. A. Interfacial chemistries 37. Mastrangeli, M., Zhou, Q., Sariola, V. & Lambert, P. Surface tension-driven for nanoscale transfer printing. J. Am. Chem. Soc. 124, 7654–7655 (2002). self-alignment. Soft Matter 13, 304–327 (2017). 12. Kim, S. Micro-LEGO for MEMS. Micromachines 10, 267 (2019). 38. Arutinov, G., Smits, E. C., Albert, P., Lambert, P. & Mastrangeli, M. In-plane 13. Linghu, C., Zhang, S., Wang, C. & Song, J. Transfer printing techniques for mode dynamics of capillary self-alignment. Langmuir 30, 13092–13102 flexible and stretchable inorganic electronics. npj Flex. Electron. 2,1–14 (2014). (2018). 39. Liu, T. L. & Kim, C. J. C. Turning a surface superrepellent even to completely 14. Wie, D. S. et al. Wafer-recyclable, environment-friendly transfer printing for wetting liquids. Science 346, 1096–1100 (2014). large-scale thin-film nanoelectronics. Proc. Natl Acad. Sci. USA 115, 40. Chen, L., Guo, Z. & Liu, W. Outmatching superhydrophobicity: bio-inspired E7236–E7244 (2018). re-entrant curvature for mighty superamphiphobicity in air. J. Mater. Chem. A 15. Zhang, Y. et al. Chemomechanics of transfer printing of thin films in a liquid 5, 14480–14507 (2017). environment. Int. J. Solids Struct. 180,30–44 (2019). 41. Liao, D., He, M. & Qiu, H. High-performance icephobic droplet rebound 16. Li, H. et al. A universal, rapid method for clean transfer of nanostructures surface with nanoscale doubly reentrant structure. Int. J. Heat. Mass Transf. onto various substrates. ACS Nano 8, 6563–6570 (2014). 133, 341–351 (2019). 17. Park, J. K. & Kim, S. Three-dimensionally structured flexible fog harvesting 42. Seo, D. et al. Rates of cavity filling by liquids. Proc. Natl Acad. Sci. 115, surfaces inspired by Namib Desert Beetles. Micromachines 10, 201 (2019). 8070–8075 (2018). 18. Park, J. K., Yang, Z. & Kim, S. Black silicon/elastomer composite surface with 43. Xu, B. et al. An epidermal stimulation and sensing platform for sensorimotor switchable wettability and adhesion between lotus and rose petal effects by prosthetic control, management of lower back exertion, and electrical muscle mechanical strain. ACS Appl. Mater. Interfaces 9, 33333–33340 (2017). activation. Adv. Mater. 28, 4462–4471 (2016). 19. Du, K., Wathuthanthri, I., Liu, Y., Xu, W. & Choi, C. H. Wafer-scale pattern transfer of metal nanostructures on polydimethylsiloxane (PDMS) substrates Acknowledgements via holographic nanopatterns. ACS Appl. Mater. Interfaces 4, 5505–5514 This work was financially supported by the National Science Foundation (Grant No. (2012). ECCS-1950009 for J.K.P. and S.K.) (Grant No. CMMI-1928788 for Y.Z. and B.X.). 20. Yoo, D., Johnson, T. W., Cherukulappurath, S., Norris, D. J. & Oh, S. H. Template-stripped tunable plasmonic devices on stretchable and rollable substrates. Acs Nano 9, 10647–10654 (2015). Author contributions 21. Jiang, D., Feng, X., Qu, B., Wang, Y. & Fang, D. Rate-dependent interaction J.K.P. and S.K. conceived the idea. J.K.P. performed the experimental studies. J.K.P. and between thin films and interfaces during micro/nanoscale transfer printing. Y.Z. carried out the analysis. J.K.P. and Y.Z. wrote the manuscript. All authors read and Soft Matter 8, 418–423 (2012). revised the manuscript. S.K. and B.X. supervised the work. 22. Chen, Y. et al. Multifunctional nanocracks in silicon nanomembranes by notch-assisted transfer printing. ACS Appl. Mater. Interfaces 10, 25644–25651 (2018). Competing interests 23. Zhang, X. C., Xuan, F. Z., Zhang, Y. K. & Tu, S. T. Multiple film cracking in The authors declare no competing interests. film/substrate systems with mismatch strain and applied strain. J. Appl. Phys. 104, 063520 (2008). Additional information 24. Chen, Z., Cotterell, B. & Wang, W. The fracture of brittle thin films on Supplementary information The online version contains supplementary material compliant substrates in flexible displays. Eng. Fract. Mech. 69, 597–603 (2002). available at https://doi.org/10.1038/s41467-021-27208-5. 25. Zhang, Y., Liu, Q. & Xu, B. Liquid-assisted, etching-free, mechanical peeling of 2D materials. Extrem. Mech. Lett. 16,33–40 (2017). Correspondence and requests for materials should be addressed to Seok Kim. 26. Zhang, Y. et al. Capillary transfer of soft films. Proc. Natl Acad. Sci. USA 117, 5210–5216 (2020). Peer review information Nature Communications thanks Stéphane Bordas, Chi Hwan 27. Hauseux, P. et al. From quantum to continuum mechanics in the Lee and the other, anonymous, reviewer(s) for their contribution to the peer review of delamination of atomically-thin layers from substrates. Nat. Commun. 11,1–8 this work. Peer reviewer reports are available. (2020). 28. Park, J. K., Eisenhaure, J. D. & Kim, S. Reversible underwater dry adhesion of Reprints and permission information is available at http://www.nature.com/reprints a shape memory polymer. Adv. Mater. Interfaces 6, 1801542 (2019). 29. Wu, S. Calculation of interfacial tension in polymer systems. J Polym Sci Part Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in C 34,19–30 (1971). published maps and institutional affiliations. 30. Yeom, J. & Shannon, M. A. Detachment lithography of photosensitive polymers: a route to fabricating three-dimensional structures. Adv. Funct. Mater. 20, 289–295 (2010). Open Access This article is licensed under a Creative Commons 31. Tas, N., Sonnenberg, T., Jansen, H., Legtenberg, R. & Elwenspoek, M. Stiction Attribution 4.0 International License, which permits use, sharing, in surface micromachining. J. Micromech. Microeng. 6, 385 (1996). adaptation, distribution and reproduction in any medium or format, as long as you give 32. Wang, Q., Chen, W. & Wu, J. Effect of capillary bridges on the interfacial adhesion of wearable electronics to epidermis. Int. J. Solids Struct. 174,85–97 appropriate credit to the original author(s) and the source, provide a link to the Creative (2019). Commons license, and indicate if changes were made. The images or other third party 33. Keum, H. et al. Microassembly of heterogeneous materials using transfer material in this article are included in the article’s Creative Commons license, unless printing and thermal processing. Sci. Rep. 6,1–9 (2016). indicated otherwise in a credit line to the material. If material is not included in the 34. Keum, H., Chung, H. J. & Kim, S. Electrical contact at the interface between article’s Creative Commons license and your intended use is not permitted by statutory silicon and transfer-printed gold films by eutectic joining. ACS Appl. Mater. regulation or exceeds the permitted use, you will need to obtain permission directly from Interfaces 5, 6061–6065 (2013). the copyright holder. To view a copy of this license, visit http://creativecommons.org/ 35. Yang, Z., Park, J. K. & Kim, S. Magnetically responsive elastomer–silicon licenses/by/4.0/. hybrid surfaces for fluid and light manipulation. Small 14, 1702839 (2018). 36. Yin, M. et al. 3D printed microheater sensor‐integrated, drug‐Encapsulated © The Author(s) 2021 microneedle patch system for pain management. Adv. Healthc. Mater. 8, 1901170 (2019). 10 NATURE COMMUNICATIONS | (2021) 12:6882 | https://doi.org/10.1038/s41467-021-27208-5 | www.nature.com/naturecommunications http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Nature Communications Springer Journals

Pattern transfer of large-scale thin membranes with controllable self-delamination interface for integrated functional systems

Loading next page...
 
/lp/springer-journals/pattern-transfer-of-large-scale-thin-membranes-with-controllable-self-n5cppyUvPn

References (50)

Publisher
Springer Journals
Copyright
Copyright © The Author(s) 2021
eISSN
2041-1723
DOI
10.1038/s41467-021-27208-5
Publisher site
See Article on Publisher Site

Abstract

ARTICLE https://doi.org/10.1038/s41467-021-27208-5 OPEN Pattern transfer of large-scale thin membranes with controllable self-delamination interface for integrated functional systems 1 2 2 1,3,4 Jun Kyu Park , Yue Zhang , Baoxing Xu & Seok Kim Direct transfer of pre-patterned device-grade nano-to-microscale materials highly benefits many existing and potential, high performance, heterogeneously integrated functional sys- tems over conventional lithography-based microfabrication. We present, in combined theory and experiment, a self-delamination-driven pattern transfer of a single crystalline silicon thin membrane via well-controlled interfacial design in liquid media. This pattern transfer allows the usage of an intermediate or mediator substrate where both front and back sides of a thin membrane are capable of being integrated with standard lithographical processing, thereby achieving deterministic assembly of the thin membrane into a multi-functional system. Implementations of these capabilities are demonstrated in broad variety of applications ranging from electronics to microelectromechanical systems, wetting and filtration, and metamaterials. 1 2 Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA. Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, VA 22903, USA. Institute for Convergence Research and Education in Advanced Technology, Yonsei University, Seoul 03722, South Korea. Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, South Korea. email: seok.kim@postech.ac.kr NATURE COMMUNICATIONS | (2021) 12:6882 | https://doi.org/10.1038/s41467-021-27208-5 | www.nature.com/naturecommunications 1 1234567890():,; ARTICLE NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-27208-5 attern transfer on a substrate is essential for the integration onto a final target substrate for functional system assembly, as of nano-to-microscale materials into functional structures depeicted in Fig. 1, which has not been shown elsewhere to our Pand devices for a wide scope of applications. For example, knowledge. The theoretical model is established to understand the 1–3 lithographical pattern transfer (e.g. photolithography , e-beam transfer mechanism based on self-delamination in the liquid 4–6 7–9 lithography , imprinting lithography , etc.) that forms a media and provides a quantitative guide to experimental photoresist pattern on a substrate has been ubiquitously utilized demonstrations in great agreement. It is worthwhile to note that in top-down monolithic microfabrication together with successive the theoretical model certainly ensures the versatility and process steps (e.g., etching and deposition). However, it suffers robustness of this method to be readily extended for other from the process specific drawbacks, such as the requirement of a membrane materials while Si membranes are primarily utilized in flat substrate and the limited material compatibility. Alternatively, this work. The membrane–substrate adhesion is controllable 10–15 direct pattern transfer via transfer printing and contact upon material selection, and thus the adhesion can be high 16–20 transfer is relatively free from those challenges since it enough to allow a lithographical process on a membrane but generates a pattern on a target substrate by conveying formerly weak enough to retrieve it from a substrate using an elastomer patterned materials that are produced on a separate mother surface. This ability provides an opportunity to build an ideal substrate. To date, these methods to transfer patterned materials patterned Si platelet array which can be deterministically on one substrate to another have been done by direct contact with assembled into function structures or devices on a target substrate 17–20 a target substrate or by a polymeric mediator that is often using transfer printing. In addition, the reported pattern transfer 16 10–13 either a spin-coated layer or a reversible dry adhesive .In method makes complex 3D Si structures possible via one-step many cases, patterned materials formed on a mother substrate transfer since a patterned Si membrane can be transferred on and after undercutting a underneath sacrificial layer are transferred to adapted for a structured target substrate due to the low flexural a target substrate by either way. In the case of transfer printing, rigidity of the membrane. As opposed to other existing direct patterned materials together with a polymeric mediator are peeled pattern transfer methods, this method enables flip and transfer of off from a mother substrate and placed onto a target substrate. a patterned membrane which grants the choice of whether an Then the removal of the polymeric mediator finishes the transfer initially patterned membrane surface faces up or down after of patterned materials to the target substrate. Although, this type transfer. This capability allows for the multiple lithographical of direct pattern transfer has been a powerful protocol to deter- processes on both front and back sides of a thin large area Si ministically assemble nano-to-microscale materials onto target membrane as shown in Fig. 1. Here, we introduce the typical substrates, the entire pattern size of a transferred material has procedure of the reported pattern transfer method and theoreti- been limited, particularly for device-grade crystalline materials cally address how interfacial force between contacting surfaces (e.g. Si, GaAs, GaN, etc.) which are highly rigid and brittle. A thin changes to allow for the pattern transfer involving thin memrance large area brittle material is commonly prone to fracture during self-delamination in different environments. Next, we demon- transfer due to strain mismatch with a target substrate or poly- strate the versatility of this method with the microassembly of 21–24 meric mediator . Thus, direct pattern transfer of a large area both single-side and double-side patterned Si platelets. Moreover, device-grade material piece without physical damage is a sig- we show the hybrid microassembly of a light emitting diode nificant challenge, which would otherwise enable more diverse (LED) circuit relying on transfer of a metal patterned Si mem- cost-effective functional integrated structures and devices. brane and surface tension-driven self-alignment. Finally, the In this work, we report a pattern transfer method that is simple and economic fabrication of challenging re-entrant enabled by self-delamination of a thin membrane from a sub- structures is exhibited. Particularly, the fabricated re-entrant strate via controlled interfacial force in liquid environments structures show omniphobicitiy and even advanced functional- particularly to directly transfer a thin and large area patterned ities such as directional omniphobicity and selective permeability single crystalline silicon (Si) membrane onto nearly any type of for filtration applications. In addition to using Si, we also used target substrate. Remarkably, the Si membrane can be litho- polyimide (PI) and designed an auxetic patterned PI membrane graphically processed on mediator substrates several times and with negative Poisson ratio to present the concept of stretch- then, in a well controlled self-delamination manner, transferred induced tunable filtration. Material 2 Si membrane (Device layer) Acetone Material 1 ② SiO ① Transfer & Remove SiO Mother 2 Mediator substrate Lithographical Self-delaminate substrate (Silanized glass) HF process (SOI) Self-delaminate Material 3 Acetone Acetone Flip & Self-delaminate Transfer & Lithographical process Fig. 1 Self-delamination based pattern transfer and its implementation into classic lithographical process of functional devices. See Supplementary Fig. 1 for the details of other variants. It starts with the initial patterning of a Si membrane on a mother substrate before transferring to a mediator substrate for subsequent processes. The processed Si memberane is flipped and transferred to another mediator substrate for further processing on the back side. Finally, the patterned Si membrane is self-delaminated from the mediator substrate and transferred to a target substrate for use. 2 NATURE COMMUNICATIONS | (2021) 12:6882 | https://doi.org/10.1038/s41467-021-27208-5 | www.nature.com/naturecommunications NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-27208-5 ARTICLE =0 =0.2 =0.4 =0.6 <0 -13 Self-delaminaon -26 0 45 90 135 180 (degree) Experiment Si/Glass/Water ( =0) Self-delamination Si/Silanized Glass/Water ( =0) Si/Glass/Acetone ( =0) Si/Silanized Glass/Acetone Theory ( =0) Si/Si/Water ( =0) No self-delamination Si/Si/Acetone ( = 0, 0.2, 0.4, 0.7) -1 Fig. 2 Theoretical model of thin film self-delamination from a substrate in liquid. a Schematic illustration of mechanics model of peeling a thin film with arrays of microscale holes and width b from a substrate in liquid by a peeling force F at a 90° degree peeling angle. b Theoretical calculations of peeling force per unit width F=b as a function of the thin film surface wettability θ for films with different ρ (total holes area over total film area), where tl G ¼ 29:4 mN/m, θ ¼ 20 , and γ ¼ 24 mN/m. c Theoretical phase diagram on the successful conditions of thin film self-delamination, which are ts sl experimentally confirmed on a wide variety of system materials for substrate, thin film, and liquid. Results and discussion membrane is modeled as a thin film with width of b peeled off from The reported pattern transfer method introduced in Fig. 1 is a substrate by a peeling force F at a 90° peeling angle in a liquid implemented in two different modes and the details are sum- environment (Fig. 2a). For a quasi-static peeling process, with a marized in Supplementary Fig. 1. The procedure starts with the small peeling distance 4l in the direction of peeling force F,the initial patterning of a Si device layer of a silicon-on-insulator energy balance between the work done by peeling force 4W and (SOI) mother substrate with HF compatible material (material 1) the change of associated surface energy 4E at the steady-state surface and forming etch holes on it. Removal of SiO layer in a HF bath transfer leads to W ¼4E ¼ F4l. When a porous film with surface porosity ρ delaminates from a substrate in liquid, the change of makes the Si device layer stick on the mother substrate. Sub- effective contact area is 4lð1  ρÞb. Therefore, the change of surface merging it in an acetone bath enables the controlled interfacial 25,26 energy is 4E ¼ G  γ ðcosθ þ cosθ Þ 4lð1  ρÞb ; force-driven self-delamination of the Si device layer, i.e., Si surface ts l tl sl where γ is liquid surface tension, θ and θ are the contact angle membrane, from the mother substrate. This is one example of the l tl sl of liquid on thin film and substrate, respectively, and reflects their theoretically designed self-delamination of a membrane from a surface wettability. G is the interfacial adhesion energy between substrate in a liquid environment which is the key to the fol- ts thin film and substrate in a dry air condition, and G ¼ γ þ γ lowing patten transfer routes. For application demonstration of ts t s γ where γ and γ arethe surfacetension of thin film and sub- the self-delaminated Si membrane, it is transferred to other ts t s strate, respectively, and γ is the interfacial tension between thin ts substrate in one of two following modes. In Mode 1, the Si film and substrate. With W ¼4E ¼ F4l, the peeling force membrane transferred on a target substrate is etched into small surface per unit width is now written as platelets using material 1 etch mask and the platelets are ready for use, which is labeled (1) in Supplementary Fig. 1. A variant of F=b ¼ðG  γ cosθ þ cosθ Þ 1  ρ : ð1Þ ts tl sl Mode 1 where the Si membrane transferred on a mediator sub- strate is lithographically processed with material 2 is labeled (2) in When the required peeling force per unit width F=b ≤ 0, Eq. Supplementary Fig. 1. The processed Si membrane may further be (1) shows that a film is self-delaminated from a substrate in transferred on the second mediator substrate after flip to process liquid, and at F=b>0, applying an external force F becomes the back side surface with material 3. The Si membrane is finally necessary for achieving the delamination. Figure 2b represents the transferred on a target substrate for use. In Mode 2, the initially plot of the required F=b along with the porosity and wettability of patterned Si membrane is transferred on a target substrate for use thin film when G ¼ 29:4 mN/m, θ ¼ 20 , and γ ¼ 24 mN/m. ts sl without further process. Similarly, Supplementary Figs. 2a, Sb show the effect of wett- The mechanics of the reported pattern transfer method involves ability of substrate and interfacial adhesion energy between thin the deterministic self-delamination of a Si membrane from a film and substrate on the required F=b, respectively. The required mother or mediator substrate via controlled interfacial force. A Si peeling strength F=b increases with the incressing of interfacial NATURE COMMUNICATIONS | (2021) 12:6882 | https://doi.org/10.1038/s41467-021-27208-5 | www.nature.com/naturecommunications 3 / (mN/m) ARTICLE NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-27208-5 adhesion energy G and F=b becomes larger than 0 for all the ts Si membrane Au pattern Au/Si platelets porosity of film when G is beyond a critical value such as the ts large van der Waals interaction force . In this scenario, applying an external mechanical peeling force is required to assist the delamination at the interface between film and substrate. As indicated in Eq. (1), a thin film is easily peeled off from a substrate in a liquid environment when the wettability is high, the film–substrate interfacial adhesion energy is low, or the porosity of a film is large. To prove this, various pairs of substrate and liquid for a Si membrane are experimentally investigated and the 5 mm 5 mm Target favorable pairs for peeling are found. As shown in Fig. 2c, the substrate theoretical diagram calculated using Eq. (1) with ρ ¼ 0 agrees well with the experiment results. In the theoretical diagram, the purple curve represents the theoretical prediction on critical condition of thin film self-delamination. The symbols represent the experimental results, where the open symbol denotes no self- delamination and the solid symbol denotes self-delamination. The colors of symbols define material types of film/substrate/ liquid. Supplementary Table 1 provides the values of parameters (G, contact angle, surface tension) which are calculated using the 28–30 harmonic mean equation . Guided by the theoretical analysis 100 μm 5 mm in Eq. (1) and the related experimental results, an acetone med- ium is selected to effectively peel a Si membrane from a Si mother Stamp substrate and a silanized glass substrate is chosen as an mediator substrate in this work. In addition, the theoretically calculated effect of porosity on F=b is experimentally proven. Si membranes with different porosity of 0.04, 0.2, 0.4, and 0.7 are prepared as shown in Supplementary Fig. 3 and the experimental results also Pick-up qualitatively shows that a higher porosity Si membrane is more favorable for peeling off from a Si substrate in an acetone med- ium. The computational modeling of the self-delamination of a film on substrates with a broad variety of materials is similar to 100 μm 100 μm that of peeling a film from substrates under an applied Mediator substrate mechanical force where molecular dynamics (MD) simulations Au/Si Si Au/Si (silanized glass) platelet can be employed . Substrate platelet Once the self-delaminated patterned thin membrane is obtained, it can be readily implemented into other processes d (outlined in Supplementary Fig. 1) for fabricating integrated functional systems. Figure 3 summarizes how Mode I (1) of the reported pattern transfer enables the production of microscale device-grade Au-coated Si platelets on a target substrate. The method begins with preparing a Si membrane with the initial pattern of deposited material (e.g. metals) on a SOI substrate (Supplementary Fig. 4a). After the complete removal of SiO sacrificial layer, the Si membrane is delaminated from a mother 100 μm SOI substrate by soaking in the acetone bath (Supplementary Fig. 4b). The Si membrane floating on liquid is transferred to a Fig. 3 Au/Si platelets on a target substrate after Mode I (1) procedure in glass target substrate with liquid (Fig. 3a left). Then drying of the Supplementary Fig. 1 and their application to microassembly via transfer underlying liquid forms tight contact between two surfaces via printing. a A schematic illustration of a Au patterned Si membrane in a rose surface tension-induced pressure 4P ¼ γ ðcosθ þ cosθ Þ=h, l tl sl mosaic shape on a target substrate before and after Si etching. b Optical where h is the distance between the Si membrane and the glass and magnified SEM images of the Au/Si platelet array. Au areas are yellow 31,32 substrate . After that, the Si membrane is dissected into an colored. c Cartoons of the microassembly of Au/Si platelets via transfer array of microscale Au/Si platelets by reactive ion etch (RIE) with printing. d A colored SEM image of assembled Au/Si platelets with the Au pattern as a hard mask (Fig. 3a, b). Consequently, a pack incremental rotations after thermal joining. Au areas are yellow colored. of aligned Au/Si platelets in various configurations regardless of the target substrate material (e.g. glass, PDMS, etc.) can be pro- duced. A rose mosaic shape pattern on a glass substrate is shown to hold Au/Si platelets but also to ensure the reliable retrieval of in Fig. 3b. Additional patterns of Au/Si platelets on glass as well as them by a polymeric stamp. Figure 3c shows this trait with car- curved PDMS substrates are shown in Supplementary Fig. 5. toons that retrieved Au/Si platelets are easily stacked without Apparently, the soft PDMS surface with a Au/Si platelet array is failure. Furthermore, these stacked Si platelets are thermally highly bendable, which envisions its potential applications toward joined by employing the eutectic bonding between Si and Au flexible electronics. surfaces to form a robust microscale structure with a unique 3D 33,34 Remarkably, the glass target substrate where a Si membrane is shape as shown in Fig. 3d . transferred and patterned may become a perfect mediator sub- Mode I (2) of the reported pattern transfer allows a Si mem- strate if it is coated with an anti-stick monolayer or silanized. brane to be attached to and detached from a mediator substrate Here, the mediator substrate is with moderate adhesion not only several times in liquid, which provides a powerful route to 4 NATURE COMMUNICATIONS | (2021) 12:6882 | https://doi.org/10.1038/s41467-021-27208-5 | www.nature.com/naturecommunications NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-27208-5 ARTICLE multiple microfabrication processes of a Si membrane as depicted electric circuit is connected and then, serially positioned RGB in the second row of Supplementary Fig. 1. Since the mediator LEDs are turned on with an external power supply. In addition, substrate needs no sacrificial layer, there is no process constraint Fig. 5c, d show that the interaction between a Si membrane and a caused by using a sacrificial layer. For example, making a Si curved target substrate transforms a 2D patterned Si membrane membrane directly from an SOI wafer does not allow depositing into a 3D structure due to the low flexural rigidity of the Si any materials incompatible with HF since it should finally be used membrane. For this purpose, a Si membrane should be thin and to remove a SiO sacrificial layer at the end of conventional Si patterned into a shape that ensures the geometric flexibility 12,18,33–35 membrane preparation protocols . In addition, via Mode (Supplementary Fig. 10a). After a Si membrane is transferred I (2), a Si membrane is easily flipped in liquid and stay upside- onto a 3D dome-shape PDMS target substrate, the strong contact down on a mediator substrate. Therefore, both front and back in between is made during the evaporation of underlying liquid. sides of the Si membrane can be processed and patterned to have The optical images and finite-element analysis (FEA) plots of 3D dual functionalities that do not interrupt each other. This ability assembled Si membranes in saddle and dome shapes depending is exceptional since conventional Si membrane preparation pro- on their initial pattern designs are shown in Figs. 5d and S10b. tocols require sophisticated patterning steps on only one side to Mode II of the reported pattern transfer also varies to allow a have multi-functions, which often sacrifices other structural pre-patterned membrane to be used on a target substrate for 12,18,33–35 performance . other novel functionalities. Figure 6 captures representative To demonstrate this exceptional ability, a double-side patterned examples of omniphobic surfaces which are built using the pat- sunflower-like Si platelet is fabricated as shown in Fig. 4a. On the tern transfer Mode II. While omniphobic surfaces have received front side, black Si and thin gold surfaces are patterned to mimic a much attention due to their repellency toward liquids with 39–43 sunflower using structural coloration and material color. On the extremely low surface tensions , forming them requires back side, a NdFeB hard magnet material is deposited and magne- complex fabrication steps since they are commonly with re- tized in one direction. The detailed process steps are available in entrant structural designs. The pattern transfer of this work may Supplementary Fig. 7. Then the double-side patterned Si platelet is provide the cost effective route to these complex re-entrant retrievedand assembledontop of a flexible PDMS pillar, which structures. Figure 6a shows a pre-patterned Si membrane that is finishes the fabrication of a sunflower-like structure with dual transferred on a continuous uncrosslinked SU8 negative photo- functionalities as shown in Fig. 4a. Due to the structural coloration, resist layer. Using an additional photomask combined with the the center portion of the Si platelet is deep black. On the other hand, transferred Si membrane enabling the self-aligned photo- the assembled structure is actuated by an external magnetic field lithography, only SU8 under rectangular openings is cured and a thanks to the strong magnetization in a NdFeB layer on the back hexagonal lattice re-entrant structure is simply constructed. This side of the Si platelet. Implementing both the structural coloration by structure is called Si/SU8 hereafter. Even simpler approach black Si and the magnetic motion by a NdFeB layer on only one side involves just a hexagonal patterned Si membrane transferred on a would be impossible as a NdFeB magnetic layer on top of black Si PDMS slab with a punched hole as depicted in Fig. 6b. The figure would diminish the structural coloration. Exceptionally, the reported shows the transfer illustrations and the image of the hexagonal Mode I (2) route to double-side processing of a Si platelet allows two patterned Si membrane on the punched PDMS slab. This struc- incompatible functionalities to reside in a single Si platelet without ture is called Si/PDMS hereafter. On these two re-entrant struc- compromising any performance. tures, even liquid with a low energy can build up an upward The tilting angle of the sunflower-like structure under an surface tension to be suspended as shown in Fig. 6c. To confirm external magnetic field B can be predicted by equating the their omniphobic characteristics, four liquids with different sur- magnetic torque V MBsin π=2  θ and the elastic restoring face tensions (γ) including water (γ = 72.8 mN/m), ethylene torque K θ, where V is the volume of a magnetic material, M is glycol (γ = 48.0 mN/m), acetone (γ = 24 mN/m), and hexane eq m a magnetization strength, K is the equivalent torsion spring (γ = 18 mN/m) are used. In addition, three different solid fraction eq hexagonal pattern designs of Si membranes and nanostructured constant, and θ is the tilting angle . As depicted in Fig. 4b, counterparts are prepared for Si/SU8 and Si/PDMS surfaces. The experimentally measured tilting angles match well with analytical geometric designs of the patterned Si membranes are in Supple- computed tilting angles, which confirms the intact magnetic mentary Fig. 11. As shown in Fig. 6d, e, all surfaces are able to motion of the Si platelet. A series of optical images of the repel relatively high surface tension liquid such as water and sunflower-like structure under different magnetic field strength ethylene glycol. However, only Si/PDMS surfaces can reliably (0, 0.55, 0.7, 0.8 T) is available in Supplementary Fig. 8. Finally, suspend liquids with very low surface tensions such as acetone Fig. 4c shows the motion of the sunflower-like structure that tilts and hexane. For Si/SU8 surfaces with the solid fraction of 0.18, upon an external magnetic field mimicking sunflower motion that those low surface tension liquids smear into the structures and tracks the sun during the daytime. forms nearly 0° contact angle showing the Wenzel state wetting as Alternatively, a pre-patterned Si membrane can be directly shown in Fig. 6e. The trend between apparent contact angle (θ ) transferred onto a target substrate where it is utilized as the final and solid fraction (f ) is theoretically predicted using the equation form, which is Mode II as depicted in the third row of Supple- of cosθ ¼ f cosθ þ 1  1 when droplets are in suspended mentary Fig. 1. Figure 5a shows a Au patterned Si membrane state , where θ is the intrinsic contact angle of water (θ = transferred on a target substrate with a disconnected red-green- 110°), ethylene glycol (θ = 85°), acetone (θ = 25°), or hexane blue (RGB) LED circuit. The optical images of a Si membrane as Y Y (θ = 5°) on a silanized either Si or SU8 surface. The solid frac- well as a target substrate are in Supplementary Fig. 9. Once a Si tion (f) of assembled surfaces are available in Supplementary membrane is delaminated from a mother substrate, the Si Fig. 12. As shown in Fig. 6d, measured apparent contact angle membrane is flipped inside a liquid medium and transferred onto values match well with theoretically calculated ones, which a target substrate. For the precision assembly, the target substrate demonstrates the deterministic omniphobic characteristics of the has a hydrophilic pattern on a square region to induce the surface re-entrant surfaces which are simply fabricated using the reported tension-driven self-alignment of the Si membrane during the pattern transfer. evaporation of underlying deionized (DI) water as shown in 36–38 When patterned Si membranes are covered with black Si Figs. 5b and S9b . The actual self-alignment procedure is nanostructures, the roughness ratio (r ) is increased to 2.8 from 1 captured in Supplementary Movie 1. After the assembly, the NATURE COMMUNICATIONS | (2021) 12:6882 | https://doi.org/10.1038/s41467-021-27208-5 | www.nature.com/naturecommunications 5 ARTICLE NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-27208-5 Fig. 4 A double-side patterned Si platelet with dual functions of structural coloration and magnetic motion after Mode I (2) procedure in Supplementary Fig. 1. a A schematic illustration of the composition of a double-side patterned Si platelet. One side is formed by black silicon nanostructures and gold patterns representing a sunflower and the other side is loaded with a NdFeB magnet alloy. The Si platelet transferred on a PDMS pillar is actuated by an external magnetic field after magnetization. b A graph showing tilting angle of the fabricated structure as a function of magnetic field strength. c Optical images for the tilting motion of the sunflower-like structure upon an external magnetic field. a Au patterned Si membrane RGB Micro LEDs 5 mm 5 mm Self-aligned transfer on hydrophilic region 1 cm Target substrate 5 mm 1 cm c d Si membrane PDMS dome Transfer on dome 4 mm 4 mm Fig. 5 An LED circuit and single crystalline Si 3D mesostructures after Mode II procedure in Supplementary Fig. 1. a A schematic illustration of the assembly process including flipping and transferring of a Au patterned Si membrane. A target substrate has a square hydrophilic region to enable the surface tension-driven self-alignment assembly. b A series of optical images of the self-alignment during underlying liquid drying and an optical image of assembled RGB LED circuit. c A schematic illustration of the process to build 3D Si mesostructures. Patterned Si membranes are transferred on structured PDMS domes. d Optical images of the resulted 3D Si mesostructures. 6 NATURE COMMUNICATIONS | (2021) 12:6882 | https://doi.org/10.1038/s41467-021-27208-5 | www.nature.com/naturecommunications NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-27208-5 ARTICLE Fig. 6 Patterned Si membranes demonstrating omniphobicity. a A schematic step to fabricate a re-entrant surface composed of a pre-patterned Si membrane on an SU8 layer involving the self-aligned photolithography. The right SEM image with brown colored SU8 structures presents the high structural integrity of the resultant Si/SU8 surface. b A schematic step to form a hexagonal patterned Si membrane on a punched PDMS. The right optical image depicts the resultant Si/PDMS surface. c Illustrations showing the upward surface tension of a low energy liquid droplet placed on Si/SU8 (upper) and Si/PDMS (lower) surfaces enabling omniphobicity. d A graph showing apparent contact angle of diverse liquids as a function of different solid fraction of Si/SU8 and Si/PDMS surfaces. e A graph showing apparent contact angle of diverse liquids as a function of their surface tension on Si/SU8 (red) and Si/PDMS (black) surfaces with f = 0.18 and f = 0.13, respectively. f A graph showing apparent contact angle of diverse liquids as a function of solid fraction of Si/PDMS surfaces. Si surfaces are either smooth (r =1, solid symbol) or nanostructured (r =2.8, hollow symbol). f f and it makes the assembled Si/PDMS surfaces superhydrophobic the auxetic lattice PI membrane increases because its Poisson’s as shown in Fig. 6f. The roughness ratio of the nanostructured ratio is negative. The ability to suspend a liquid droplet is surface is measured using an AFM technique and is found in inversely proportional to the lattice dimension (L ). With the Supplementary Fig. 13. However, the roughness ratio acts dif- negative Poisson’s ratio, the mechanical stretch-induced switch- ferently for liquids with lower surface tension (θ < 90°), and able omniphobicity is achieved in the auxetic lattice PI membrane causes the reduced omniphobicity. This difference is explained as opposed to conventional grid pattern surfaces. To show this capability, a droplet of vegetable oil is placed and suspended on using the equation of cosθ ¼fr cosθ þ 1  1 that is used f Y both hexagonal and auxetic lattice PI membranes. Then the for a solid surface with a roughness . Apparently, the negative membranes are uniaxially stretched and only the oil droplet on cosθ term for a lower surface tension (θ < 90°) liquid decreases Y Y the auxetic lattice PI membrane penetrates it. The detailed cosθ . Figure 6f does not include data for hexane which is chal- experimental results are captured in Supplementary Movie 2. lenging for the nanostructured Si/PDMS surface to reliably Remarkably, the assembled Si/PDMS surface shown in Fig. 6 suspend. demonstrates the switchable wettability macroscopically Furthermore, inspired by the simple Si/PDMS surface fabri- depending on the configuration of the assembly although its cation step presented in Fig. 6, a mechanical metamaterial made microscopic wettability is still omniphobic. When a Si membrane of PI is designed to show the stretch-induced switchable wett- is facing upward as depicted in left column of Fig. 7b, the mac- ability. Here, auxetic (metamaterial sample) and hexagonal roscopic wettability is dictated by the property of PDMS (control sample) patterned PI membranes are transferred and (hydrophobic and oleophilic) as a liquid droplet meets with the bonded to a punched PDMS slab. The fabrication steps for PI underneath punched PDMS sidewall. Here, a 500 μm-thick PI membranes are available in Supplementary Fig. 14. When the sheet is added to ensure the structural rigidity of the assembled hexagonal lattice PI membrane is uniaxially stretched, the lattice surface. Therefore, vegetable oil (γ = 32 mN/m) pass through the dimension (L ) normal to the stretching direction decreases assembled surface. On the other hand, when the Si membrane is because of its positive Poisson’s ratio (Fig. 7a). However, that of NATURE COMMUNICATIONS | (2021) 12:6882 | https://doi.org/10.1038/s41467-021-27208-5 | www.nature.com/naturecommunications 7 ARTICLE NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-27208-5 Stretch-induced switchable omniphobicity 0 % uniaxial strain 40 % uniaxial strain Hexagonal lace 100 μm 100 μm 3 mm Auxec lace 100 μm 100 μm b Directional omniphobicity Veg Oil Veg Oil Si membrane PI backbone PDMS PDMS PI backbone Si membrane Oleophilic & Omniphobic 1 cm 1 cm Hydrohpobic (c) Selective chloroform/water filtration Water Chloroform Chloroform Water Si membrane Si membrane PDMS PDMS PI backbone PI backbone Oleophilic & Oleophilic & Hydropohbic Hydropohbic 1 cm 1 cm Fig. 7 PI membranes showing stretch-induced switchable omniphobicity, and hexagonal patterned Si membranes demonstrating directional omniphobicity and selective filtration. a Illustrations and images of PI membranes with auxetic lattice design for novel stretch-induced switchable wettability and with counterpart hexagonal lattice design. b An assembled oleophilic Si/PDMS/PI surface where vegetable oil passes (left) and an omniphobic PI/PDMS/Si surface where vegetable oil does not pass (right). c Selective filtration of chloroform/water mixture using the assembled oleophilic yet hydrophobic Si/PDMS/PI surface where chloroform passes, yet water is trapped. facing down as depicted in right column of Fig. 7b, the assembled is controlled by the material underneath the patterned Si mem- surface becomes purely omniphobic as liquid does not meet any brane, other variations are also possible by changing the under- other surfaces under the Si membrane. Consequently, vegetable neath material. Supplementary Fig. 15 and Supplementary oil does not pass through the assembled surface. More demon- Movie 5 depict one of the variations where the assembled surface strative experimental results are available in Supplementary is omniphilic using a water and oil permeable material, such as Movie 3. TexWipe under the Si membrane. While the assembled Si/ The straightforward application of these unique capabilities of PDMS surface show promising potentials towards directional the assembled Si/PDMS/PI surface should be to separate water wettability and resultant filtration applications, its functionalities from low surface tension liquids. As a part of example, the are from unique structural designs enabled by the simple pattern mixture between water (γ = 72.8 mN/m) and chloroform transfer methods presented in this work. (γ = 27 mN/m) is prepared and poured into the assembled sur- This work reports the unique capabilities of a thin membrane face where a Si membrane is facing upward as shown in Fig. 7c. pattern transfer method which relies on determinate control of Since the macroscopic wettability of the assembled surface is interfacial force between contacting surfaces in liquid environ- oleophilic and hydrophobic, chloroform passes through the ments and theoretical explanations to understand key parameters assembled surface and is collected in an underneath container determining optimal membrane-substrate–liquid combinations. while water is trapped on top of the assembled surface. Supple- Particularly, a pre-patterned device-grade single crystalline Si mentary Movie 4 presents more details of the experimental membrane is easily transferred to nearly any type of substrates results. Since the macroscale wettability of the assembled surface encompassing a silanized glass mediator substrate for use or 8 NATURE COMMUNICATIONS | (2021) 12:6882 | https://doi.org/10.1038/s41467-021-27208-5 | www.nature.com/naturecommunications NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-27208-5 ARTICLE further microfabrication processes. Upon these unique cap- the Si membrane with Au/Cr pattern (Supplementary Fig. 9a) is flipped inside acetone bath and moved to DI water bath. After that, the Si membrane transferred abilities, the versatility of this approach is summarized by onto the hydrophilic region with DI water. DI water is let dried for 24 h to ensure demonstrating the microassembly of single- and double-side tight contact is made between the Si membrane and the target substrate. RGB LEDs patterned Si membranes, the hybrid assembly of RGB LED circuit (SMD 0603, Dialight) are connected to the assembled circuit using silver epoxy especially assisted with the surface tension-driven self-alignment. (8331S, MG chemicals). Finally, 10 V is applied to turn the LED lights on through soldered copper wire. Moreover, re-entrant shape patterned surfaces are straightfor- To build single crystalline Si 3D mesostructures, an SOI device layer (3 μm) is wardly and cost-effectively fabricated for surface directional patterned by using SF (20 sccm) and O (2 sccm) plasma with 150 W at 20 mTorr 6 2 omniphobicity and selective filtration purposes, which highlights for 6 min with photoresist as masking layer (Supplementary Fig. 10a). PDMS dome the potential of the reported approach towards diverse applica- structures are prepared by pouring 10:1 base to curing agent ratio PDMS precursor (Sylgard 184, Dow Chemical) on a mold. Then the Si membranes are transferred tions. Future opportunities include extending thin membrane onto the cured PDMS dome structures with underlying liquids. Here the outer ring material choices possibly using guidance from further theoretical in Supplementary Fig. 10a is used to manually align an Si membrane and a PDMS models and enabling more precision assembly processes dome structure and is removed after contact. employing advanced equipment and tooling. Fabrication of omniphobic Si/SU8 surfaces. Negative photoresist (SU8-50, Microchem) is spun on a Si substrate with 3000 rpm and soft baked at 65 °C for Methods 5 min and at 95 °C for 15 min. This yielded 40 μm-thick soft baked SU8 layer on a Fabrication and transfer of Si membrane with Au pattern. Fabrication of a Si Si substrate. A separately prepared pre-patterned Si membrane is delaminated from membrane starts with rinsing an SOI wafer (3 μm-thick device layer and 1 μm- its mother substrate in acetone bath and transferred to IPA bath for selectivity. thick SiO sacrificial layer) with acetone, IPA, and DI water followed by drying Then it is transferred to the soft baked SU8 layer. Drying out the underlying IPA under a stream of nitrogen. Cr (5 nm)/Au (50 nm) is deposited using e-beam and subsequent heating on 65 °C for 5 min makes conformal contact between SU8 evaporation (FC-2000, Termescal) onto the device layer of SOI wafer and wet and the SI membrane. After that, 200 mJ/cm of UV light is selectively exposed to etched through a mask of photoresist (AZ5214, Microchem) as shown in Sup- rectangular openings, which defines supporting SU8 pillars connected to the Si plementary Fig. 3a. Then the Si device layer is patterned into a desired shape using substrate. The assembled substrate is hard baked at 65 °C for 1 min and 95 °C for SF (20 sccm) and O (2 sccm) plasma at 150 W, 20 mTorr for 6 min. After that, 6 2 5 min. Using SU8 developer (Microchem), SU8 is developed to define rectangular the sample is immersed in HF bath for 6–12 h to remove the SiO sacrificial layer. pillar. The resultant structure surface is modified by depositing silane (Tri- The patterned Si membrane is delaminated from the mother SOI substrate by chloro(1H,1H,2H,2H,-perfluorooctyl)silane, Sigma Aldrich). immersing in acetone bath as shown in Supplementary Fig. 4b. Then the floating Si membrane is scooped with acetone and transferred onto a target substrate. Drying of underlying liquid completes the pattern transfer of a Si membrane with Au Fabrication of hexagonal and auxetic lattice PI membranes. PMMA (PMMA pattern. A7, Microchem) is spun on a Si wafer at 3500 rpm for 40 s and baked at 180 °C for 3.5 min. Then PI (PI-2545, Dupont) is spun on the PMMA layer at 2000 rpm for 60 s and cured at 250 °C in a vacuum oven. This yields a 3 μm-thick PI layer with sufficient Patterning of Si membrane into Au/Si platelets and transfer printing of Au/Si thickness uniformity. Cr (5 nm)/Au (20 nm) is deposited by e-beam evaporation (FC- platelets. Once a Si membrane with Au pattern is transferred on a target substrate. 2000, Temescal) onto the PI layer and wet etched through a mask of photoresist The Si membrane is dissected into Au/Si platelets using SF (20 sccm) and O 6 2 (AZ5214, Microchem) as the PI layer to have hexagonal or auxetic designs (Supple- (2 sccm) plasma at 150 W, 20 mTorr for 6 min with the Au pattern as an etching mentary Fig. 14a). Using the Cr/Au layer as an etch mask, the PI and PMMA layers mask as shown in Supplementary Fig. 6. When the target substrate is a silanized are dry-etched using an O plasma at 20 sccm with 200 W at 50 mTorr for 10 min glass substrate, Au/Si platelets on it are easily picked up using a PDMS stamp. The (Supplementary Fig. 14b). Then the sample is immersed in acetone bath for 24 h to PDMS stamp is brought into contact with a Si platelet with preload and rapidly remove the PMMA sacrificial layer and release the PI membrane from the wafer. The retracted to pick up a Au/Si platelet. The Au/Si platelets are transferred to another PI membranes are transferred onto punched PDMS slabs to suspend hexagonal or target Si substrate with translation and angular alignment to build a stacked auxetic design parts (Supplementary Fig. 14c). Then the assembled surface is cut into a structure shown in Fig. 3d. After stacking, the Au/Si platelets are thermally joined stretchable shape (Supplementary Fig. 14d). in rapid thermal processing (RTP) furnace at 360 °C for 10 min. Data availability Fabrication of sunflower mimicking structure. A device layer of an SOI wafer All data used and generated in this study are available in Supporting Information. (10 μm-thick device layer and 1 μm-thick SiO sacrificial layer) is partially patterned with black Si nanostructures. To pattern black Si nanostructure, native oxide on Si surface is removed in HF bath for 1 min. Then thin oxide layer was grown by O Received: 10 August 2021; Accepted: 3 November 2021; plasma at 10 sccm, RF1 120 W, RF2 200 W at 50 mTorr for 5 min. The oxide layer is incompletely etched by CHF plasma at 12 sccm, 350 W at 50 mTorr for 2 min. Using the left oxide islands as an etching mask Si is slowly etched by Cl (40 sccm) and Ar (4 sccm) plasma RF1 250 W, RF2 300 W at 90 mTorr for 10 min to form sharp and dense nanostructures. Then the Si membrane is patterned by DRIE process such that a Si platelet array is mechanically supported by the Si membrane (Supplementary Fig. 7a). Then the Si membrane is delaminated and flipped from the mother substrate References inside the liquid medium, and transferred on a silanized glass substrate. On the glass 1. Bratton, D., Yang, D., Dai, J. & Ober, C. K. Recent progress in high resolution substrate, Cr (5 nm)/Au (50 nm) is patterned by a lift-off process with a photoresist lithography. Polym. Adv. Technol. 17,94–103 (2006). masking layer (SPR220, Microchem). Once the front side process is finished, the Si 2. Pimpin, A. & Srituravanich, W. Review on micro-and nanolithography membrane is delaminated again in acetone bath (Supplementary Fig. 7b) and trans- techniques and their applications. Eng. J. 16,37–56 (2012). ferred to a new silanized glass substrate for backside processing as depicted in Sup- 3. Wu, B. & Kumar, A. Extreme ultraviolet lithography: a review. J. Vac. Sci. plementary Fig. 7c. On the Si membrane, Ti (10 nm)/NdFeB (400 nm)/Ti (10 nm) are Technol. B 25, 1743–1761 (2007). sputter deposited. After the deposition, the NdFeB layer is magnetized under 1.9 T 4. Chen, Y. Nanofabrication by electron beam lithography and its applications: a magnetic field and delaminated from the glass substrate (Supplementary Fig. 7d). After review. Microelectron. Eng. 135,57–72 (2015). transfer to another new silanized glass substrate, a Si platelet is mechanically unteth- 5. Tseng, A. A., Chen, K., Chen, C. D. & Ma, K. J. Electron beam lithography in ered form the Si membrane and picked up by a PDMS pillar to be a sunflower nanoscale fabrication: recent development. IEEE Trans. Electron. Packag. mimicking structure (Supplementary Fig. 7e, S7f). Manuf. 26, 141–149 (2003). 6. Altissimo, M. E-beam lithography for micro-/nanofabrication. Biomicrofluidics 4, 026503 (2010). Fabrication of LED circuit and single crystalline Si 3D mesostructures.To 7. Kooy, N., Mohamed, K., Pin, L. T. & Guan, O. S. A review of roll-to-roll build a LED circuit, Cr (5 nm)/Au (20 nm) is deposited by e-beam evaporation nanoimprint lithography. Nanoscale Res. Lett. 9,1–13 (2014). (FC-2000, Temescal) on a SOI device layer (3 μm) and a Si wafer. Then the 8. Schift, H. Nanoimprint lithography: 2D or not 2D? A review. Appl. Phys. A deposited layers are wet etched through a mask of photoresist (AZ5214, Micro- 121, 415–435 (2015). chem) as shown in Supplementary Fig. 9. To fabricate a Si membrane, a gold- patterned SOI wafer device layer is etched by SF (20 sccm) and O (2 sccm) 9. Balla, T., Spearing, S. M. & Monk, A. An assessment of the process capabilities 6 2 plasma with 150 W at 20 mTorr for 6 min. To pattern a square hydrophilic region of nanoimprint lithography. J. Phys. D 41, 174001 (2008). on a target substrate, a mask of photoresist is patterned on the square area and 10. Carlson, A., Bowen, A. M., Huang, Y., Nuzzo, R. G. & Rogers, J. A. Transfer silane (Trichloro(1H,1H,2H,2H,-perfluorooctyl)silane, Sigma Aldrich) is selectively printing techniques for materials assembly and micro/nanodevice fabrication. deposited using the photoresist as a masking layer (Supplementary Fig. 9b). The Adv. Mater. 24, 5284–5318 (2012). target substrate is cleaned with acetone and IPA to remove the masking layer. Then NATURE COMMUNICATIONS | (2021) 12:6882 | https://doi.org/10.1038/s41467-021-27208-5 | www.nature.com/naturecommunications 9 ARTICLE NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-27208-5 11. Loo, Y. L., Willett, R. L., Baldwin, K. W. & Rogers, J. A. Interfacial chemistries 37. Mastrangeli, M., Zhou, Q., Sariola, V. & Lambert, P. Surface tension-driven for nanoscale transfer printing. J. Am. Chem. Soc. 124, 7654–7655 (2002). self-alignment. Soft Matter 13, 304–327 (2017). 12. Kim, S. Micro-LEGO for MEMS. Micromachines 10, 267 (2019). 38. Arutinov, G., Smits, E. C., Albert, P., Lambert, P. & Mastrangeli, M. In-plane 13. Linghu, C., Zhang, S., Wang, C. & Song, J. Transfer printing techniques for mode dynamics of capillary self-alignment. Langmuir 30, 13092–13102 flexible and stretchable inorganic electronics. npj Flex. Electron. 2,1–14 (2014). (2018). 39. Liu, T. L. & Kim, C. J. C. Turning a surface superrepellent even to completely 14. Wie, D. S. et al. Wafer-recyclable, environment-friendly transfer printing for wetting liquids. Science 346, 1096–1100 (2014). large-scale thin-film nanoelectronics. Proc. Natl Acad. Sci. USA 115, 40. Chen, L., Guo, Z. & Liu, W. Outmatching superhydrophobicity: bio-inspired E7236–E7244 (2018). re-entrant curvature for mighty superamphiphobicity in air. J. Mater. Chem. A 15. Zhang, Y. et al. Chemomechanics of transfer printing of thin films in a liquid 5, 14480–14507 (2017). environment. Int. J. Solids Struct. 180,30–44 (2019). 41. Liao, D., He, M. & Qiu, H. High-performance icephobic droplet rebound 16. Li, H. et al. A universal, rapid method for clean transfer of nanostructures surface with nanoscale doubly reentrant structure. Int. J. Heat. Mass Transf. onto various substrates. ACS Nano 8, 6563–6570 (2014). 133, 341–351 (2019). 17. Park, J. K. & Kim, S. Three-dimensionally structured flexible fog harvesting 42. Seo, D. et al. Rates of cavity filling by liquids. Proc. Natl Acad. Sci. 115, surfaces inspired by Namib Desert Beetles. Micromachines 10, 201 (2019). 8070–8075 (2018). 18. Park, J. K., Yang, Z. & Kim, S. Black silicon/elastomer composite surface with 43. Xu, B. et al. An epidermal stimulation and sensing platform for sensorimotor switchable wettability and adhesion between lotus and rose petal effects by prosthetic control, management of lower back exertion, and electrical muscle mechanical strain. ACS Appl. Mater. Interfaces 9, 33333–33340 (2017). activation. Adv. Mater. 28, 4462–4471 (2016). 19. Du, K., Wathuthanthri, I., Liu, Y., Xu, W. & Choi, C. H. Wafer-scale pattern transfer of metal nanostructures on polydimethylsiloxane (PDMS) substrates Acknowledgements via holographic nanopatterns. ACS Appl. Mater. Interfaces 4, 5505–5514 This work was financially supported by the National Science Foundation (Grant No. (2012). ECCS-1950009 for J.K.P. and S.K.) (Grant No. CMMI-1928788 for Y.Z. and B.X.). 20. Yoo, D., Johnson, T. W., Cherukulappurath, S., Norris, D. J. & Oh, S. H. Template-stripped tunable plasmonic devices on stretchable and rollable substrates. Acs Nano 9, 10647–10654 (2015). Author contributions 21. Jiang, D., Feng, X., Qu, B., Wang, Y. & Fang, D. Rate-dependent interaction J.K.P. and S.K. conceived the idea. J.K.P. performed the experimental studies. J.K.P. and between thin films and interfaces during micro/nanoscale transfer printing. Y.Z. carried out the analysis. J.K.P. and Y.Z. wrote the manuscript. All authors read and Soft Matter 8, 418–423 (2012). revised the manuscript. S.K. and B.X. supervised the work. 22. Chen, Y. et al. Multifunctional nanocracks in silicon nanomembranes by notch-assisted transfer printing. ACS Appl. Mater. Interfaces 10, 25644–25651 (2018). Competing interests 23. Zhang, X. C., Xuan, F. Z., Zhang, Y. K. & Tu, S. T. Multiple film cracking in The authors declare no competing interests. film/substrate systems with mismatch strain and applied strain. J. Appl. Phys. 104, 063520 (2008). Additional information 24. Chen, Z., Cotterell, B. & Wang, W. The fracture of brittle thin films on Supplementary information The online version contains supplementary material compliant substrates in flexible displays. Eng. Fract. Mech. 69, 597–603 (2002). available at https://doi.org/10.1038/s41467-021-27208-5. 25. Zhang, Y., Liu, Q. & Xu, B. Liquid-assisted, etching-free, mechanical peeling of 2D materials. Extrem. Mech. Lett. 16,33–40 (2017). Correspondence and requests for materials should be addressed to Seok Kim. 26. Zhang, Y. et al. Capillary transfer of soft films. Proc. Natl Acad. Sci. USA 117, 5210–5216 (2020). Peer review information Nature Communications thanks Stéphane Bordas, Chi Hwan 27. Hauseux, P. et al. From quantum to continuum mechanics in the Lee and the other, anonymous, reviewer(s) for their contribution to the peer review of delamination of atomically-thin layers from substrates. Nat. Commun. 11,1–8 this work. Peer reviewer reports are available. (2020). 28. Park, J. K., Eisenhaure, J. D. & Kim, S. Reversible underwater dry adhesion of Reprints and permission information is available at http://www.nature.com/reprints a shape memory polymer. Adv. Mater. Interfaces 6, 1801542 (2019). 29. Wu, S. Calculation of interfacial tension in polymer systems. J Polym Sci Part Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in C 34,19–30 (1971). published maps and institutional affiliations. 30. Yeom, J. & Shannon, M. A. Detachment lithography of photosensitive polymers: a route to fabricating three-dimensional structures. Adv. Funct. Mater. 20, 289–295 (2010). Open Access This article is licensed under a Creative Commons 31. Tas, N., Sonnenberg, T., Jansen, H., Legtenberg, R. & Elwenspoek, M. Stiction Attribution 4.0 International License, which permits use, sharing, in surface micromachining. J. Micromech. Microeng. 6, 385 (1996). adaptation, distribution and reproduction in any medium or format, as long as you give 32. Wang, Q., Chen, W. & Wu, J. Effect of capillary bridges on the interfacial adhesion of wearable electronics to epidermis. Int. J. Solids Struct. 174,85–97 appropriate credit to the original author(s) and the source, provide a link to the Creative (2019). Commons license, and indicate if changes were made. The images or other third party 33. Keum, H. et al. Microassembly of heterogeneous materials using transfer material in this article are included in the article’s Creative Commons license, unless printing and thermal processing. Sci. Rep. 6,1–9 (2016). indicated otherwise in a credit line to the material. If material is not included in the 34. Keum, H., Chung, H. J. & Kim, S. Electrical contact at the interface between article’s Creative Commons license and your intended use is not permitted by statutory silicon and transfer-printed gold films by eutectic joining. ACS Appl. Mater. regulation or exceeds the permitted use, you will need to obtain permission directly from Interfaces 5, 6061–6065 (2013). the copyright holder. To view a copy of this license, visit http://creativecommons.org/ 35. Yang, Z., Park, J. K. & Kim, S. Magnetically responsive elastomer–silicon licenses/by/4.0/. hybrid surfaces for fluid and light manipulation. Small 14, 1702839 (2018). 36. Yin, M. et al. 3D printed microheater sensor‐integrated, drug‐Encapsulated © The Author(s) 2021 microneedle patch system for pain management. Adv. Healthc. Mater. 8, 1901170 (2019). 10 NATURE COMMUNICATIONS | (2021) 12:6882 | https://doi.org/10.1038/s41467-021-27208-5 | www.nature.com/naturecommunications

Journal

Nature CommunicationsSpringer Journals

Published: Nov 26, 2021

There are no references for this article.