Reversible Bubble Transfer on a Bioinspired Tridirectionally Anisotropic Lubricant-Infused Surface

Abstract

Underwater bubble transfers on functional surfaces with special wettability have important research value for many fields such as water purification, gas-evolving electrochemistry, heterogeneous catalysis, etc. However, realizing multi-interface collaborated and multi-directional bubble transfers are still challenging. Herein, inspired by butterfly wings, pitcher plants, and rice leaves, we present a tridirectionally anisotropic lubricantinfused surface (TALIS) with micro−nano hierarchical step-like structures that are covered with silicone oil. The TALIS exhibits significant tridirectional anisotropy in terms of bubble sliding, specifically, the slippery property parallel to the grooves with an ultra-low bubble sliding angle (BSA) of ∼2°, and the unidirectional wettability perpendicular to the grooves with BSA difference of ∼48°result from the step-edge pinning effect. By adjusting the step height and width, TALISs with different tridirectionally anisotropic wettability and stable bubble-holding efficiency (∼0.4 mg/cm 2 ) are obtained. In addition, horizontal and anti-buoyancy unidirectional bubble transfers are realized by collaborative squeezing of two face-to-face TALISs. By adjusting the distance between the two TALISs, bubbles can be reversibly transferred between the two interfaces by multi-interfaces collaboration. This work opens a new avenue to understand the bubble behaviors on functional interfaces with anisotropic wettability and provides a method to realize controllable bubble transfer on multi directions.