Tunable wetting surfaces with interacting cavities via femtosecond laser patterning and wet etching

Abstract

This paper presents the production of bioinspired slippery glass surfaces with interacting cavities via wet-etching-assisted femtosecond laser fabrication. A femtosecond laser irradiates a glass surface to fabricate microvoid arrays inside the substrate. Then, wet etching is performed to induce microcavities on the sample surface. With laser-induced selective etching, the region below the substrate surface is etched faster, thereby developing microcavities. The microvoid separation distance is found to be important for controlling the contact angle (CA) of the liquid wetting the surface. By choosing an adequate microvoid separation distance and etching time, interacting/interconnected cavities can be successfully fabricated. CAs are expected to be tuned from almost 0 degrees to 137 degrees +/- 2.5 degrees based on the cavity separation distance and the processes used (laser patterning, etching, and silanization). These interconnected structures fabricated with small separation distances (e.g., 10 mu m) can lock in an infused lubricating liquid and form a stable, inert, slippery interface, known as a slippery liquid-infused porous surface, which acts as a smooth cushion for liquid repellence. Moreover, the infused liquid can significantly increase the transmittance owing to the index matching effect. Such slippery surfaces could be used in several self-cleaning, optical-sensing, and biomedical applications.