Robust Smart Superhydrophobic Cilia.

As inspired by natural cilia, smart (stimuli-responsive) artificial microwires can manipulate objects and tune surface properties, leading to various applications. However, artificial microwires operate merely in gentle working conditions due to their inherent fragility against mechanical damage, indicating that there is a critical gap between the microwires demonstrated in a laboratory and the microwires that operate in practical conditions. This inherent limitation is circumvented by introducing a new surface design, where the microwires are hidden in interconnected frames when facing mechanical damage and can be aroused by external magnetic fields to deliver functionalities when needed. Namely, under a magnetic field parallel to a substrate textured with vertical frames, iron-laden polydimethylsiloxane (PDMS) aerosols are aligned perpendicularly onto frame sidewalls, forming multilayer microwires parallel to the substrate. The frames prevent mechanical damage from contacting the wires, and the lower layers of wires are functional, although the top layers are worn off, rendering the mechanical robustness. By applying a magnetic field, the wires can re-align uprightly and hence expose themselves to the working environment, delivering functionalities such as on-demand control in droplet impact dynamics, adhesion force, and transport. This design strategy paves the way for the utilization of smart surfaces in real-life conditions.