Self-Motion of a Benzoquinone Disk Coupled with a Redox Reaction

Self-motion is one of the most promising systems for achieving mechanical function in an inanimate system. In this Article, a change in the mode of self-motion coupled with a redox reaction is reported as a novel autonomous system. A solid disk of benzoquinone (BQ, oxidant) spontaneously moved on a solution of reductant (ascorbic acid or potassium ferrocyanide K4[Fe(CN)6]), and the mode of self-motion, that is, continuous motion → intermittent motion (repetition between rest and rapid motion) → velocity-decay mode, changed depending on the concentration of the reductant. The concentration region for the motion of K4[Fe(CN)6] was broader than that for ascorbic acid. The characteristic features of motion are discussed in relation to surface tension as the driving force and the reaction kinetics of BQ. The present BQ system can be expanded to be controlled by various external fields, such as in electrochemical, photochemical, and biochemical reaction systems.