Stretchable superhydrophobic elastomers with on-demand tunable wettability for droplet manipulation and multi-stage reaction

Superhydrophobic surfaces with tunable wettability are critical for miniaturized reaction systems with promising applications in point-of-care diagnostics, liquid droplet micro-reactors, non-loss manipulation, and surface-enhanced Raman scattering sensing. However, the design and demonstration of stretchable superhydrophobic surfaces with on-demand transitions in wettability remain challenging. In this study, we report a facile approach to fabricating stretchable superhydrophobic surfaces with different microstructures (arc-shaped or V-shaped air pockets) for multi-stage liquid droplet micro-reactors. The surfaces with arc-shaped air pockets are kept in the stable Cassie-Baxter state enabling droplet micro-reactions, whereas the surfaces with V-shaped air pockets that go through pressure-induced Cassie-Baxter to Wenzel transitions facilitate the transport of droplets in between reactions. The low-cost and scalable fabrication method with the effective design strategy provided by this work also paves the way for broad applications that range from liquid droplet micro-reactors and manipulations to chemical detection and analysis in stretchable microfluidic devices.