Engineering frog-skin-inspired wrinkled self-lubricative liquid-like interfaces on biodegradable plastics

Abstract

Hypothesis: Colloid and interface science increasingly seeks strategies to control liquid-solid interactions through surface engineering and lubricant confinement. Biomimetic surfaces with designed lubricant-confined patterns and ultra-low adhesion to sticky fluids have garnered increased attention due to their broad applicability across numerous engineering fields. Although technologies for manufacturing silicone-based coatings are well established, the fabrication of fluorine-free slippery coatings that offer robust oil-storing capability without complex micro-texturing remains challenging.

Experiments: Inspired by frog skins, we engineered a multifunctional, self-lubricative interface decorated with random micro-sized structured wrinkles and nanochannels by simultaneous physical and chemical conjugation of vinyl-terminated polydimethylsiloxane (PDMS) with a controlled amount of low-viscosity silicone oil on starch-based bioplastics via a facile, cost-effective, and scalable process. We reasoned that the synergistic lubrication effects provided by the PDMS chains and silicone oil promoted strong swelling and integration, thereby ensuring super-lubricity.

Findings: The oil-bearing, self-lubricative coating readily slid water and other low-surface-tension liquids, resisted adhesion of multicomponent viscous fluids such as honey and tomato ketchup, delayed ice formation by up to 240 s, and showed high optical transparency (>80 %). The judicious infiltration of silicone oil into the PDMS chains resulted in low sliding angles of 10° (ethanol) and 8° (n-hexadecane) and enabled sticky honey to slide at 0.12 cm s^-1 when the surface was titled at 75°. This work introduces a simple, low-cost, universal and non-fluorinated strategy to construct robust, patterned slippery coatings with liquid-like characteristics for a wide range of food-contact applications.

Keywords: Bioplastics; Lubricated surfaces; Polydimethylsiloxane; Self-lubricative; Slippery surfaces; Surface engineering.