Physics / mechanism
Hydrophobic coatings repel water via high contact angles (>90°); oleophobic coatings extend this to low-surface-tension oils. Mechanism is surface energy reduction — fluorinated silanes (PFAS-based or PFAS-free alternatives), fluoropolymer films, or nanostructured surfaces create Cassie-Baxter states where liquid sits on air pockets rather than wetting the substrate. Key parameters: water contact angle (WCA; lotus-effect surfaces >150°), contact angle hysteresis (<5° for low roll-off), abrasion durability (Taber cycles to failure), and optical transmission loss (critical for photonic and display applications). SOTA commercial coatings (AGC Cytop, Daikin Optool, Apple’s proprietary iPhone lens treatments) achieve WCA ~115–120° on glass with <0.5% transmission loss. Regulatory pressure on long-chain PFAS is forcing reformulation across the supply chain.
Competitive landscape
Fluoropolymer deposition (CVD/ALD fluorocarbon) competes directly with solution-phase silane coatings. Atomic layer etching to create re-entrant nanostructures (no chemistry required) is an emerging alternative for semiconductor-adjacent applications. Plasma-polymerised coatings offer better adhesion than silanes but lower WCA. Omniphobic surfaces (repel both water and oils below 30 mN/m) remain primarily academic.
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.