Patterned hydrophilic and hydrophobic surface chemistry for tunable wetting control on silicone substrates
Surface engineering technology that patterns hydrophilic PEG microdomains within a hydrophobic PDMS background to create smooth biphilic 'slippery covalently attached liquid-like surfaces' (SCALS). By varying PEG/PDMS area fraction, domain size, and spacing, the surface tunes its apparent wetting angle, enabling controlled transitions between spreading, pinning, smearing, transfer, and roll-off. This helps silicone test surfaces better mimic skin-like fluid interaction while preserving soft, durable polymer mechanics.
Overview
This technology addresses a key limitation of silicone test surfaces: they mimic skin softness but not skin-like fluid behaviour. By patterning hydrophilic PEG microdomains within a hydrophobic PDMS background, the surface gains controlled chemical heterogeneity at the microscale. The result is a smooth biphilic "slippery covalently attached liquid-like surface" (SCALS) that can be tuned so aqueous fluids bead, spread, pin, smear, or transfer in designed ways.
Control is chemical and microscale, not rough texture, so soft contact mechanics are preserved. The covalently attached liquid-like layers are more durable than loose coatings or infused liquids and require no complex topology.
Technical specifications
The photolithographic fabrication route includes UV-ozone activation, PDMS vapour deposition and methyl-capping, resist removal, reactivation, and PEGylation, yielding defined PEG/PDMS area fractions, domain sizes, and spacings.
Key features:
- Tunable apparent wetting angle via PEG/PDMS area fraction
- Controlled pinning, smearing, transfer, and roll-off behaviour
- Ultralow contact angle hysteresis on both chemistries
- Covalently attached layers for improved durability
- Preserves soft polymer mechanics without complex topology
- Targets skin-relevant COF of 0.4–0.6
Validation approach:
- Contact angle and hysteresis measurements
- Tilt-stage roll-off testing for wetting and pinning
- Skin-relevant complex fluid tests under controlled load and shear
- Comparison with unmodified silicone and benchmarks
- Pattern iteration for durability and cleanability after repeated use
Technology readiness level
Early research stage with a defined validation pathway. Planned work includes fabricating silicone coupons with patterned PEG/PDMS SCALS, producing a matrix of pattern parameters, and characterising wetting behaviour. The goal is to optimise skin-like wetting, pinning, transfer, durability, and cleanability, targeting a COF of 0.4–0.6.
About University of Edinburgh
The University of Edinburgh is a comprehensive, research‑intensive public university in Scotland’s capital. Industry engages through co‑located facilities and innovation hubs that bring companies into the university ecosystem, including the Bayes Centre for data and AI and the Usher Institute at the Edinburgh BioQuarter. Integration with NHS Lothian at BioQuarter places hospital care, clinics and university research on a single site to speed clinical studies and translation. Research is supported by competitive UK government funding via UKRI and Innovate UK, alongside major charitable funders such as Wellcome. A dedicated technology transfer company, Edinburgh Innovations, streamlines access to expertise, IP management, licensing and venture creation.
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