Silicon gels with sustainable self-replenishment: Fluid drag reduction through viscosity dependency

Slippery liquid infused surfaces (SLISs) provide excellent dynamic lubrication properties by storing the lubricant internally to form a homogeneous liquid layer to insulate external ambient fluids. However, the kinetic instability caused by lubricant depletion gradually degrades the surface slippery performance. Herein, inspired by skin gland secretion system, silicon gels with sustainable self -replenishment were prepared using polydimethylsiloxane (PDMS) and commercially available dimethyl silicone oils. By carefully tuning the kinematic viscosity and content of infused oil, the surfaces of corresponding silicon gels demonstrated significant syneresis behavior, and the lubricating oils released from the surface were still detected after continuous wiping for more than 120 days. More importantly, when the ratio of working fluid to infused oil was 6.8, the maximum drag reduction of silicon gel in Couette flow could reach up to about 16%, while the surfaces remained long-lasting water repellency under the continuous shear action of encapsulated water. Self-replenishable silicon gels exhibiting strong kinetic stability were expected to provide valuable design insights for robust slippery interfaces.