Bio-inspired smart surface to achieve controllable locomotion through adjustable anisotropic friction

Anisotropic friction generated by microstructured surfaces is crucial for performing functions such as directional locomotion and adhesion in biological systems.Hence,an epoxy-based shape memory polymer(SMP)incorporating Fe_(3)O_(4) nanoparticles is used in this study to create a smart surface with oriented structures to mimic anisotropic friction and exploit human-developed controllable locomotion systems.Applying the specific properties of the epoxy-based SMP,fast switching friction can be achieved by adjusting the topography and stiffness of the microstructures on the surface.In addition,the photothermogenesis effect of Fe_(3)O_(4) nanoparticles induces changes in the asymmetric topography and stiffness on the SMP surface under the irradiation of near-infrared(NIR)light,thereby inducing a rapid switching of the friction force.Furthermore,a microbot is created to demonstrate remotely controlled locomotion,such as unidirectional and round-trip movements,and braking by switching the friction force under NIR light.These results are promising for the design of new intelligent surfaces and interfaces;additionally,they may facilitate the investigation of biological structures and processes.

Poly(N-isopropylacrylamide)-based thermo-responsive surfaces with controllable cell adhesion

Poly(N-isopropylacrylamide)(PNIPAAm)-based thermo-responsive surfaces can switch their wettability(from wettable to non-wettable) and adhesion(from sticky to non-sticky) according to external temperature changes. These smart surfaces with switchable interfacial properties are playing increasingly important roles in a diverse range of biomedical applications; these controlling cell-adhesion behavior has shown great potential for tissue engineering and disease diagnostics. Herein we reviewed the recent progress of research on PNIPAAm-based thermo-responsive surfaces that can dynamically control cell adhesion behavior. The underlying response mechanisms and influencing factors for PNIPAAm-based surfaces to control cell adhesion are described first. Then, PNIPAAm-modified two-dimensional flat surfaces for cell-sheet engineering and PNIPAAm-modified three-dimensional nanostructured surfaces for diagnostics are summarized. We also provide a future perspective for the development of stimuli-responsive surfaces.

Dynamic metal patterns of wrinkles based on photosensitive layers

Regulating metal surfaces with micro-/nanoscale structures is of great significance for both material science and potential applications.However,the intrinsic properties of metals,such as fixed isotropic moduli and inflexible structures,in a sense present major limitations in developing next-generation smart patterned surfaces.In this work,a facile and general patterning strategy is proposed to endow insensitive metal surfaces with controllable spontaneous topologies and dynamic performance by exquisitely introducing an essential photosensitive interlayer.The arresting anthracene-containing photocrosslinking interlayer can selectively predetermine the anisotropic property of compliant bilayers without damaging metals’homogeneous properties,and realize a changeable stiff/soft layer.Furthermore,the mechanical transition mechanism of the self-adaptive wrinkling modes in metalbased trilayer systems is revealed to pave the pathway for regulating functional wrinkled metal surfaces.This photodriven metal patterning strategy can promote the development of brand-new methods for tuning the instability of multilayered materials,and be potentially applied in smart optical devices with dynamic reflectance,including light gratings and"magic"mirrors.