Hybrid covalent graft and microtexture for skin-like fluid transfer on PDMS

Overview

This solution is a tunable hybrid surface treatment for polydimethylsiloxane (PDMS) elastomers, designed to mimic the fluid-transfer behavior of human skin. It combines two surface features: shallow, rounded microtexture that pins contact lines and creates temporary reservoirs for aqueous fluids, and a covalently attached neutral hydrophilic graft placed mainly in protected valleys. The silicone ridge caps bear mechanical contact, protect the modified regions, and help maintain friction.

The design addresses a key limitation of unmodified silicone: it dewets and allows fluids to roll off too quickly. By introducing chemical heterogeneity and topographic edges, the surface resists rapid dewetting and roll-off, retains complex aqueous fluids during application, and promotes controlled smear and transfer under shear. Because the graft is located primarily in protected valleys, it is less exposed to direct abrasion and reduces the risk of an over-hydrated, low-friction surface.

Technical specifications

Key features:

• Hybrid surface combining microtexture and patterned covalent hydrophilic graft
• Open, rounded ridges and valleys provide contact-line pinning and temporary fluid reservoirs without closed pores that trap cleaner
• Graft placed mainly in valleys to reduce abrasion and maintain friction
• Covalent attachment overcomes the short-lived effect of plasma activation alone
• Tunable parameters include texture geometry, modified area fraction, graft composition, thickness, and crosslink density
• Low-extractable, fully cured PDMS substrate with controlled post-cure, rinsing, and residual analysis reduces bloom and tack drift
• Chemistry-only, texture-only, uniform-graft, and untreated controls separate mechanisms and support a practical fallback route

Technology readiness level

The technology is at an early research stage. The proposed 26-week validation program will establish two reproducible, open, skin-relevant texture levels and a covalent grafting window, then fabricate an 18–24 condition library to screen residuals and pattern fidelity. Dynamic wetting, pinning, roll-off, smear and transfer, friction, chemistry, and topography will be measured to down-select three candidates. Two finalists will then be optimized and reproduced across three independent lots and subjected to combined wear, cleaning, product-conditioning, migration, tack, and aging challenges. Delivery includes release data, SOPs, cleaning and storage guidance, QC limits, and a scale-up route, supporting progression toward pilot or production use.