Light-induced Patterning and Grafting for Slippery Surfaces based on Silane-coated Nanoporous Structures

This protocol describes a light-induced method for fabricating spatially patterned slippery surfaces via digital light processing (DLP) and polymerization-induced phase separation. A photocurable polyurethane acrylate (PUA) resin is mixed with a water-soluble porogen (PEG-200) and selectively exposed to ultraviolet (UV) light using a DLP projection system. This process simultaneously induces polymer crosslinking and porogen phase separation. After porogen removal, a nanoporous structure remains, which is chemically modified via UV-ozone activation and vapor-phase silanization to enhance hydrophobicity. Silicone oil is then infused and covalently grafted onto the surface using multi-wavelength UV light, forming a stable polydimethylsiloxane (PDMS) brush layer. The resulting surface exhibits strong liquid repellency, low contact angle hysteresis, and high optical transparency. Wettability is quantitatively evaluated using contact angle and hysteresis measurements with water, octane, honey, and artificial human saliva. This method enables selective slipperiness, demonstrated by directing water-based droplets away from slippery domains toward untreated hydrophilic regions, forming well-defined liquid patterns. The approach supports high-resolution, maskless fabrication on flexible substrates and scalable patterning for applications in microfluidics, droplet transport, water harvesting, and biomedical devices.