Laser-induced morphology-switchable slanted shape memory microcones for maneuvering liquid droplets and dry adhesion

Abstract

Slanted micro-/nano-structures play pivotal roles in a diversity of fields, including water-proof engineering and fogdrop collection. In light of recent advances in fabricating slanted microstructures by using photolithography or reactive ion etching techniques, however, a complex, environmentally unfavorable, and tedious fabrication process makes them far from practical in application. Herein, we present a viable strategy to prepare a slanted shape memory microcone array (SSMMA) by combining the femtosecond laser oblique microfabrication and replica-mold method. Thanks to its fast temperature-responsive feature, SSMMA enables the transition of adhesion forces to effectively control the sliding of droplet on the surface. The underlying principle of the adjustable migration behavior of droplet is that SSMMA switches between the slanted and collapsed states. Moreover, we systematically studied the influence of the microcone spacing/height together with the microcone bending angle on the wetting performance of water droplet. More significantly, the resulted SSMMA analogous to a “machine hand” is experimentally demonstrated to be competent for the grab and transfer of fragile and smooth objects (e.g., coverslip) with a maximum adhesion force of ∼19.404 mN. The current study opens up an avenue for rapidly fabricating functional slanted microstructures for practical usage.