Chapter 6: Physical Chemistry of Energy Conversion in Self-propelled Droplets Induced by Dewetting Effect

Active matter, which mimics the remarkable complexity of living organisms, converts a local energy supply from the surrounding environment to locomotion in a homogeneous concentration field. Perpetual energy conversion and consumption serve to keep active matter out of thermal equilibrium. The dynamics of the energy conversion and consumption processes involve physicochemical interactions with the surrounding environment. This chapter focuses on the physicochemical properties of self-propelled droplets as a typical example of artificial active matter. Sections 6.2 and 6.3 present the foundations of the thermodynamics of energy-converting droplets. Section 6.4 describes the experimental studies of the spontaneous running motion originating from the wetting effect. The knowledge derived from experimenting with various systems using different solvents, solutes, and surfactants, can provide clarification on the predominant factors and the mechanisms of the phenomenon.