Erasable and Programmable Unidirectional Liquid Transport on Multiple Asymmetric Slippery Microstructures

Unidirectional fluid delivery on an asymmetric microstructure has garnered significant attention due to its advantages, such as being pumpless, multifunctional, and easy to integrate. However, the precise design of continuous flow in unidirectional transport and on-surface recyclable manipulation remains challenging. Here, we present a 3D-printed array of multiple asymmetric microstructures decorated with a nanoparticle-based sprayable slippery coating that can achieve promising liquid control for both droplets and flow. Inspired by two biological modes, lizard skin and butterfly wings, we designed two types of asymmetric microstructures, i.e., triangular protrusions and tilted microcones. Both asymmetric microstructures exhibit unidirectional wettability, such as directional droplet sliding and liquid spreading. Benefiting from the improved water repellency of the slippery surface, asymmetric microstructures can unlock more functions compared to previous examples, such as erasable liquid channels, programmable flow control, and modular fluidics. By tuning the motion resistance of the asymmetric microstructure, a complex and diverse pathway for the unidirectional channel is achieved, such as ordered flow transport and flow-based logic circuits for LED lighting. This contribution unifies two types of asymmetric microstructures in one system, providing a deeper analysis of resistance tuning in unidirectional fluid transport. We envision that these slippery asymmetric microstructures will diversify liquid-manipulating interfaces for the development of advanced fluidic devices.