Cortical‐Folding‐Inspired Multifunctional Reduced Graphene Oxide Microarchitecture Arrays on Curved Substrates

Abstract

and low-cost method, surface wrinkling of thin films on soft substrates has been developed to generate various functional micro/nanostructures (e.g., wrinkles, creases, crumples, and folds) on planar and curved substrates. [13][14][15][16] These wrinkling structures with tunable surface-wetting, electronical, and mechanical properties bring great potentials for emerging applications including flexible electronics, [17][18][19] reversible patterning, [20][21][22] smart wetting surfaces, [23][24][25] and actuators. [26,27] Compared with traditional microfabrication methods, surface wrinkling shows advantages (e.g., template-free, simple, and low-cost) in the fabrication of microarchitecture arrays on curved substrates. [15] Many efforts have been put into the controlled wrinkling of metal coatings, polymer films, and oxide layers on curved surfaces through thermal shrinkage, [28,29] negative pressure, [30,31] and swelling/ deswelling. [32,33] Due to fascinated thermal, electrical, and optical properties, strain engineering of 2D materials has become a hot research topic. [34,35] Graphene oxide (GO), because of excellent flexibility and rich oxygen-containing groups, is suitable to form conformal coatings on various curved substrates. [36,37] Diverse functional wrinkled structures have been achieved via the wrinkling of GO films on spherical and cylindrical substrates, such as highly-convoluted patterns for deforming actuators, [27] hierarchical ridges for strain sensors, [38,39] and multigenerational crumples for anticounterfeiting patterns. [40] Recently, inspired by the hierarchical papillae of the rose petal, we obtained superhydrophobic papillae arrays by the wrinkling of nonuniform GO films coated on spherical latex substrates. [8] Although it provides a feasible method for fabricating hierarchical architecture arrays on curved substrates, there are still some issues: i) Only millimeter-scale architectures (>0.6 mm) could be obtained because of the restriction of the coating technique, which limits their applications in largearea micro/nanofabrication of architecture arrays on curved substrates. ii) The previous work mainly focuses on the surfacewetting properties of the papillae whereas mechanical stability of the wrinkled papillae arrays has not yet been demonstrated. iii) Most importantly, although the wrinkling of single-layer stiff or soft films on curved substrates has been investigated, [15,27,31] the folding of stiff/soft bilayers with large modulus contrast Although controlled wrinkling is demonstrated to be a powerful tool for micro/nanofabrication, large-area fabrication of microarchitecture arrays on curved substrates by surface wrinkling still remains challenging. Inspired by the cortical folding, a facile method for transforming graphene oxide (GO) patterns into multiscale microarchitecture arrays on curved substrates is developed. Mass production of hierarchical GO papillae arrays can be realized by homogeneous compression of patterned GO/rubber bilayers. The reduced GO (rGO) papillae arrays sho...

Multifunctional Biomimetic Microstructured Surfaces for Healthcare Applications

“…Inspired by the cortical fold structure, Chu et al proposed a strategy to convert patterned films directly into 3D hierarchical microarchitecture arrays on curved substrates through a spontaneous folding process. [86] The deflation step allows the generation of layered papillae arrays with tunable feature sizes that exhibit controllable superhydrophobic properties. The realization of the change in the morphology and size of the microstructure can also be achieved by applied stimuli such as temperature, mechanical strain, magnetic field, and electric field.…”

Efficient Fabrication of Carbon Nanotube‐Based Stretchable Electrodes for Flexible Electronic Devices

“…In this study, based on the previous works of our group, [34,36,37] a simple shrinking method was proposed to prepare a CNT-based stretchable electrode. The electrode was fabricated by coating a CNT aqueous dispersion on an inflated latex balloon, drying, and deflating.…”