Hierarchical silicone grooves for oil/water pinning and squeeze-flow drainage

Overview

This research program develops molded silicone coupons with hierarchical surface textures that couple capillary pinning with deformation-driven squeeze flow to control liquid retention, drainage, and friction. The surface design combines larger grooves that direct drainage with smaller recesses and edges that regulate liquid retention and release during rubbing.

These surfaces are engineered to maintain stable lubricated friction, targeting a sliding coefficient of 0.4-0.6, while managing the transfer and retention of aqueous fluids, oils, and emulsions. By tuning feature dimensions and silicone elasticity, the approach balances capillary retention with viscous drainage, offering a path to surfaces with predictable wetting and friction behavior in fluid-contact applications.

Technical specifications

Key features:

• Hierarchical ridges, grooves, and recesses molded directly into silicone coupons, avoiding reliance on replenishing additives
• Larger grooves direct drainage while smaller recesses and edges regulate liquid retention and release
• Feature dimensions and elasticity tune contact area and drainage times during rubbing
• Quantification of contact-angle hysteresis, residual liquid area, and lipid smear/transfer before and after shear
• Evaluation of how adsorbed skin- or formulation-derived lipids alter wetting and friction
• Performance tested across aqueous fluids, oils, and emulsions
• Durability assessed over months of storage in varied environments and repeated compressive shear cycles

The research foundation includes published work showing that silicone pattern dimensions and bending regulate lubricated friction, and prior findings demonstrating phospholipid adsorption onto PDMS from contacting fluids. Validation will include fabricating a coupon library that varies ridge aspect ratio, contact area fraction, groove connectivity, and recess depth, with composition-matched flat controls, verified by profilometry and microscopy.

Technology readiness level

This technology is at an early research stage. Planned validation includes defining test conditions (silicone modulus, coupon dimensions, skin benchmark, representative fluids, counterface, load, speed, and cleaning protocol); characterizing advancing and receding contact angles, contact-line pinning, drainage kinetics, and residual wetted area under compression and shear; coupling measurements to friction maps to identify geometries balancing capillary retention and viscous drainage; and tracking storage aging and repeated shear durability. Deliverables include coupons, fabrication specifications, test protocols, and performance and durability data for comparative evaluation.