Bioinspired multi-asymmetric magnetized surfaces for tailoring energy-free liquid manipulation and 3-DOF solid transportation

Abstract: Through the utilization of smart materials and well-designed structures, functional surfaces have been developed to enable small-scale liquid/solid manipulation tasks, thereby facilitating crucial applications in the fields of microfluidics, soft robotics, and biomedical engineering. However, the design of functional systems with flexible, tunable, and multimodal liquid/solid manipulation capabilities remains a challenging endeavor. Here, inspired by asymmetric structural features in natural plants and metachrony in cross-scale biological systems, I report a magnetic-responsive functional surface that can achieve rich liquid operations under static magnetic fields, while also enabling the transportation of solids with multiple degrees of freedom (DOFs) under dynamic magnetic fields. The presence of curvature pillars on the surface, combined with their magnetic-driven tilt/gradient arrangement, imparts liquids with multi-directional spreading modes based on the asymmetry of Laplace pressure. I elucidate the mechanisms governing these liquid spreading modes and subsequently develop compelling liquid operations, such as adjustable anti-gravity climbing, spontaneous modal shifts in liquid transport, and liquid mixing. Furthermore, the dynamic metachronal motion of the magnetic pillars can be harnessed for solid object transportation. I illustrate the synchronous/asynchronous transport modes of the surface and propose a novel strategy for achieving 3-DOF solid transportation by coordinating the arrangement of objects and employing magnetic actuation strategies. This study presents a new design concept for application-oriented manipulation surfaces, which hold significant potential for extensive engineering applications.