Wetting Detachment for Dry Adhesives

Bioinspired dry adhesives relying on van der Waals forces exhibit promising potential in robotic manipulation. However, existing artificial adhesives for object manipulation necessitate external energy inputs (mechanical loads/physical fields) to drive attachment-detachment switching, i.e., non-spontaneous switching behavior, which makes it challenging to achieve a combination of rapid response and a wide range of manipulable payloads. Here, inspired by the prey-capturing phenomenon of Nepenthes, we propose a surface wettability-based adhesion strategy termed “wetting detachment for dry adhesives”. This approach leverages microfluidics to regulate the intervening medium, i.e., the substance between the adhesive microstructures and the target surface, enabling spontaneously switchable adhesion without mechanical loads or external physical fields. Driven by surface wettability, an external liquid can spontaneously flow into micro-channels naturally formed by the contact between the adhesive and the target surface, and spread into the adhesive interface to form a fully-covered liquid film, causing a dramatic reduction in adhesion (minimum adhesion: 0.92 kPa). Following liquid volatilization, the adhesive recovers its original adhesion (maximum adhesion: 141 kPa), accomplishing a remarkable adhesion switching ratio of 153. The attachment-detachment response time reaches the millisecond scale, which enables efficient manipulation of objects ranging from 1-mg scale to kilogram scale. This innovative strategy imparts excellent attachment-detachment switchability to adhesives, thereby opening new avenues for the development of dry adhesive-based devices and systems.