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Potential Memory Effects in Self-Moving Oil Droplets
Takashi Ikegami, Naoto Horibe and Martin M. Hanczyc

A series of chemical experiments have been designed to investigate the emergence of spontaneous self-movement in a simple chemical system consisting of oil droplets using oleic anhydride as fuel. Using spatial and temporal droplet tracking, we analyzed in detail the motion of single droplets in an aqueous environment. In particular we note that the variation in a single droplet’s behavior, analyzed as the stop-go interval, displays a power law distribution indicating bias in behavior. In addition, the rate of movement of the droplet in comparison to the diffusion rate of chemical reaction products in the system may affect the movement of the droplet resulting in long time scale memory effects. These discoveries illustrate that coupling a chemical reaction (hydrolysis of the anhydride) to a physical body (the oil droplet) can result in an instability that affects many aspects of the droplet system, from reaction rate to convective flow patterns to overall shape to macroscopic behavior.

Keywords: Oil droplet, convection flow, self-motion, memory

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