Acoustic Assembly Photopolymerization of Bioinspired Multifunctional Devices With Programmable Adhesion

Abstract Devices with stimuli-responsiveness, programmable and reversible adhesion, and adaptability to uneven surfaces have attracted extensive attention for applications such as micro-gripper and soft robots. Despite advances in design and manufacturing, challenges still exist in rapid shape morphing, non-contact control, and reversible switching between attachment and detachment. Fundamentally, those challenges are owing to the material limitation, manufacturing constraints, and design complexity involved in the production of those devices. To overcome these challenges, we report a simple and rapid manufacturing approach, acoustic assembly photopolymerization (AAP), for the production of magnetic-responsive devices with programmable and reversible adhesion. The proposed AAP process provides an environmentally sustainable approach to fabricating micro- to macro-scale multimaterial films within seconds. The locally controlled multimaterial composition enables precise magnetic control, while the flexible hierarchical surface structures allow rapid attachment and detachment. The combined effects of material and structural composition enable remarkable control over the adhesive property without requiring any complicated treatment and power source. In this work, a photocurable magnetic composite material was developed, and the adhesion and magnetic responsive characteristics of the printed films were further investigated. As a proof-of-concept, two test cases were performed using the as-printed films. The first test case is soft magnetic robots made of AAP-printed films. Effects of the film surface structures on the adhesive properties and hence the robot crawling locomotion are analyzed. The second test case is a gripper for lifting and releasing objects. Capability of the AAP-printed films on gripping objects of different sizes in different environments (i.e., in air and in water) are demonstrated. Experimental results validated the effectiveness of the novel AAP process on fabricating films with spatially varied compositions and hierarchical surface features. The test cases indicated the promising applications of such AAP-printed films, with advantages of programmable adhesion, locally-engineered flexibility, rapid and remote non-contact magnetic actuation. The AAP manufacturing capability and the proposed multimaterial hierarchical surface design possess a broad range of applications, including surface engineering, soft robotics, and microfluidics.