Development of electrically conductive-superoleophobic micropillars for reducing surface adhesion of oil at low temperatures

Abstract

Electrically conductive and superoleophobic micropillars have been developed through the construction of biomimetic micropillars using Ag-filled epoxy composites and the incorporation of FDTS on the micropillar surface. These micropillars are found to be superoleophobic with an oil contact angle of 140°, demonstrating excellent self-cleaning properties. The conductivity of micropillars allows for the Joule-heating effect to actively reduce the adhesion and even unfreeze the frozen oil droplets by passing electrical current. Electrical resistance of the composite micropillars was modulated by two orders of magnitudes by varying the contents of Ag flakes from 45wt% to 65wt%. The effectiveness of conductive micropillars for surface un-freezing was investigated by applying DC current to decrease the adhesion strength of frozen oil droplets on surfaces. The results showed a pronounced reduction of frozen oil adhesion force by 60% when the resistance increased from 7.5Ω to 877Ω after applying DC current for 2min. By continuously applying DC current for 3min, the frozen oil adhesion decreased to 0.05N, reaching zero when the surface was heated up to −10°C after applying DC current for 5min. In contrast, when the droplet was heated up to −5°C by hot air, there is still a substantial force of adhesion. The research findings demonstrate the use of constructing conductive-superoleophobic composite micropillars at surface for eliminating the frozen oil from surfaces at low temperatures.