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

Abstract

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 Fe3O4 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 Fe3O4 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.

Precise Controlling of Friction and Adhesion on Reprogrammable Shape Memory Micropillars

“…Furthermore, the friction coefficient can be well switched between the values of ∼0.8 and ∼1.2, even in a very small region, revealing that the precise control of fraction behaviors was realized. To our knowledge, such a report on the precise control within an extremely small area (0.90 mm 2 ) has been rarely reported. , …”

“…To our knowledge, such a report on the precise control within an extremely small area (0.90 mm 2 ) has been rarely reported. 43,44 To further explore the mechanism of the significant difference in friction behaviors, the wear scars were analyzed through a scanning electron microscope, as shown in Figure 4a. Obviously, the width of the wear scar was ∼150 μm on the compressed surface; in contrast, the wear scar width on the recovered surface increased to ∼1000 μm, nearly 7 times higher than that of the compressed surface (Figure 4b).…”

Earthworm‐Inspired Soft Skin Crawling Robot

“…[ 9 , 10 , 11 ] Asymmetric microstructures on surfaces are oriented at specific angles to the supporting layer, creating directional anisotropy in the friction response along the movement direction. [ 12 , 13 , 14 ] Examples of anisotropic friction include the highly ordered microstructures found in various biological systems, such as reptiles, [ 15 , 16 ] insects, [ 17 , 18 , 19 ] and worms, [ 20 , 21 , 22 , 23 ] exhibiting high friction forces for propulsion and low friction forces for sliding. The magnitude of anisotropic friction depends primarily on surface topography, the ratio of sample–substrate stiffness, the aspect ratio of surface structures, and substrate roughness.…”

Shape Memory Polyurethane Composite With Fast Response to Near‐Infrared Light Based on Tannic Acid–Iron and Dynamic Phenol‐Carbamate Network

“…[23][24][25] To address these issues, researchers have undertaken various efforts, such as modifying fillers to enhance compatibility or using fillers with better compatibility. [26] Yet, this would bring about some issues such as waste of resources and complicated preparation processes. Undoubtedly, it is imperative to fabricate SMPUs with rapid NIR light responsiveness through a straightforward approach.…”