Printed hydrophilic domains on thiol-ene silicone for durable skin-like wetting

Overview

This technology is a photo-cured silicone material engineered to mimic the wetting behavior of human skin. Real skin is neither uniformly hydrophilic nor uniformly hydrophobic – it pins fluids through a combination of surface chemistry patches and micro-scale furrows. This silicone reproduces that behavior by creating sparse, covalently bonded hydrophilic domains on a hydrophobic, skin-textured silicone matrix. The result is a surface on which drops do not readily roll or spread, closely matching the behavior of fluids on skin, while preserving skin-like friction and avoiding the slippery, fully hydrated surfaces of continuous hydrogels.

The approach is intended for use in skin simulants, in vitro testing substrates, consumer-product evaluation, and any application needing durable, skin-like fluid handling. Because the hydrophilic domains are covalently grafted and printed in precise registration with the surface texture, the wetting behavior is designed to persist through rubbing, cleaning, and accelerated ageing.

Technical specifications

How it works:

• A silica-reinforced thiol-ene silicone is photo-cured into a coupon with a skin-like surface texture and a thin, thiol-rich surface layer.
• Digital-light projection is used to print poly(N,N-dimethylacrylamide) domains, tens of microns wide, covering 10–40% of the surface area.
• The domains are grafted through surface thiols and interlock a few microns into the silicone, forming a covalent attachment rather than a weak coating.
• After grafting, residual thiols are capped, and unreacted monomers, initiators, and oligomers are extracted and verified to limit contamination and hydrophobic recovery.

Key features:

• Hydrophilic domains pin the receding contact line, increasing contact-angle hysteresis without making the whole surface hydrophilic.
• The hydrophobic silicone matrix and texture preserve a high advancing contact angle and skin-like friction.
• Covalent grafting addresses common failure modes such as delamination, pattern loss, and time-dependent loss of wettability.
• The design avoids the very low wet coefficient of friction of continuous hydrogel skins.

Technology readiness level

The technology is in an active research and development phase. A 12-month program is planned that will screen domain size, coverage, and depth for target fluids, then validate durability through rubbing, cleaning, accelerated and light-exposed ageing, extractables testing, and tack measurements. The final stage will produce reproducible coupons with standard operating procedures, quality-control specifications, and real-time ageing data. An optional extension includes a second optimization loop, a 50-coupon pilot batch, and 12 months of additional real-time data. Interim coupons are expected to support early pre-screening within six months.