Bioinspired milliscale near-boundary undulatory motion for fluid transport and adhesive locomotion

Abstract

Gastropods use pedal waves to transport thin fluid films at the body-substrate interface. Inspired by this strategy, we present a near-boundary pumping mechanism using magnetically actuated, prebuckled undulatory sheets. Through theoretical modeling and experimental validation, we systematically analyze how design, actuation, and fluid properties influence wave propagation and transport performance of a single unit under full and partial immersion. We then demonstrate that optimized temporal and spatial phase shifts among multiple units notably enhance fluid transport. Leveraging these insights, we develop miniature devices for planar and tubular transport. We further integrate this mechanism into a soft crawling millirobot that uses snail-like adhesive locomotion. This robot can traverse slippery surfaces across various inclinations and liquid coatings, as well as uneven, mucus-covered gastrointestinal tissues, with speeds surpassing its biological counterparts. These findings highlight the potential of bio-inspired near-boundary transport for next-generation medical devices and millirobots.