Triple-Bioinspired Shape Memory Microcavities with Strong and Switchable Adhesion.

Smart adhesives with switchable adhesion have attracted considerable attention for their potential applications in sensors, soft grippers, and robots. In particular, surfaces with controlled adhesion to both solids and liquids have received more attention, because of their wider range of applications. However, surfaces that exhibit controllable adhesion to both solids and liquids often cannot provide sufficient adhesion strength for strong solid adhesion. To overcome this limitation, this study developed a triple-bioinspired shape memory smart adhesive, drawing inspiration from the adhesion structures found in octopus suckers, lotus leaves, and creepers. Our adhesive design incorporates microcavities formed by a shape memory polymer (SMP), which can transition between rubbery and glassy states in response to temperature changes. By leveraging the shape memory effect and the rubber-glass (R-G) phase transition of the SMP, the adhesion of the surface to smooth solids, rough solids, and water droplets could be switched by adjusting the temperature and applied force. Notably, the adhesives designed herein exhibited high adhesion strength (up to 420 kPa) on solids, facilitated by the shape interlocking effect and the negative pressure generated within the microcavities. Furthermore, the programmable transport of solids and liquids can be achieved by utilizing this switchable adhesion. This approach expands the possibilities for designing smart adhesives and holds potential for various applications in different fields.