Anomalous spontaneous entropy reduction phenomenon in oil droplet diffusion

Abstract

Entropy inherently tends to increase in the absence of external influence, leading to greater disorder. Herein, the anomalous spontaneous entropy reduction phenomenon was found, as demonstrated by the spontaneous aggregation of floating oil. Specifically, the polytetrafluoroethylene (PTFE) film after laser treating (LT-PTFE) possesses superhydrophobic (a water contact angle of ∼153.5°) and superoleophobic (an oil contact angle of ∼152.0°) properties. Once floating oil came into contact with the LT-PTFE surface, it was adsorbed and spread on it. Ultimately, the oil and water completely separated, achieving floating oil spontaneously aggregated into spherical shapes. We conducted a comprehensive analysis of the critical parameters influencing the movement of both floating oil and water, including floating oil volume, water film thickness, and substrate surface characteristics. Through theoretical calculations and fluid dynamics simulations, the factors essential for the manifestation of this phenomenon were elucidated. We posit that this discovery represents a significant advancement in spontaneous entropy reduction behavior and offers innovative insights into integrating entropy reduction with experimental approaches.