Adhesion switchable transition on bio-inspired Janus surface for multi-directional droplet manipulation

Abstract

Achieving precise and rapid droplets manipulation in versatile directions transport remains a considerable challenge, however adhesion switchable transitions deemed to be rather serviceable. Here, a double-sided microplate array (DMPA) with bio-inspired Janus surfaces, is proposed to fulfill adjustable adhesion through surface wettability switching and microplate dynamic deformation, thereby executing the droplet multi-dimensional manipulation in response to dynamic magnetic field. The triple-coupled bio-inspired Janus surfaces are newly designed with a convex hull and striped structure respectively, inspired by the respiratory ciliary motion and surface properties of lotus and rice leaves. Leveraging variation in superhydrophobicity and low adhesion of convex hull side on Janus surface, diverse droplet directional transports are achieved in plane, such as high-speed horizontal transport (120 mm/s and 500 µL), anti-gravitational climbing (inclined by 15°), and selective droplet orientation. The adhesion switchable transition of surface striped structure on other side is predominated by solid–liquid contact lines evolution resulting from microplate bending deformation, realizing droplet capture/release for long-distance multi-dimensional transport. Concurrently, a magnetic-responsive droplet switch is developed based on multi-directional droplet manipulation, demonstrating enormous potential for practical application.