Skin-like wetting on silicone via molded microrelief and grafted pinning domains

Overview

Silicone and skin can share similar surface energy yet handle fluids differently: silicone's receding contact angle stays high and droplets retract, while skin pins and smears fluid via microrelief and chemical heterogeneity. This hybrid surface treatment combines a molded, skin-like microrelief with sparsely grafted hydrophilic pinning domains.

The design enables largely independent control of wetting and friction. The microrelief reduces real contact area, bringing the coefficient of friction into the 0.4–0.6 skin-contact range, while discrete hydrophilic domains act as contact-line pinning defects governing droplet spreading, smearing, and fluid retention. Texture is part of the bulk and chemistry is covalently bound — no unbound layer to bloom or drift.

Technical specifications

Three established techniques are combined:

• Solvent extraction of uncrosslinked oligomers — removes a major cause of hydrophobic recovery, blooming, and tack drift.
• Molded skin-like microrelief — cuts real contact area, bringing coefficient of friction into the 0.4–0.6 range and adding geometric pinning sites.
• Sparse hydrophilic domains covalently grafted via a patchy silica-like interlayer or direct hydrosilylation — contact-line pinning defects sized and distributed per pinning theory.

Discrete domains tolerate strain better than continuous films, and a low grafted area fraction limits hydration lubrication. Unlike single treatments — brushes, plasma, or roughness alone — this hybrid tunes wetting and friction largely independently.

Validation uses ISO 25178 areal topography (Sq and Sdr vs. friction; Sdr and Vvc vs. pinning and fluid retention), dynamic contact angles, high-speed imaging, tribometry, XPS/FTIR, and probe tack.

Technology readiness level

At approximately TRL 3, a 12-month, three-phase validation program is planned: establish the extraction protocol and fabricate replica and engineered masters; screen a matrix of topography and chemistry variants for wetting, smear, and friction, down-selecting three candidates; then test durability under rubbing, washing, and storage and deliver optimized prototype coupons with a final report. Commercial-scale manufacturing is not yet demonstrated.