Induction of electromotive force by an autonomously moving magnetic bot

We report the observation of the induction of electromotive force (emf) into a Faraday coil by an autonomously moving composite magnetic particle in aqueous medium. The particle consisted of a micron-sized polymer sphere, which was decorated with catalytic Pd nanoparticles (NPs) and attached to a micron-scale (N-42 grade) rare-earth magnet. The Pd NPs catalytically decomposed H2 O2 to generate O2 , resulting in buoyancy-driven vertical motion of the particle, while the micromagnet induced emf during the flight. Because a small volume of ethanol was layered on top of the liquid, the bubble burst when the particle ascended to the top and thus nearly continuous vertical motion was achieved. Spikes of alternating electrical signal could be observed up to 20 times per minute. The signal was sufficiently strong to illuminate light-emitting diodes following appropriate amplification. This distinctive approach is expected to pave the way to developing synthetic bots which are autonomously propelled, generating their own signal for running complex circuitry.