Complex magnetic fields breathe life into fluids

Abstract

The vast majority of materials research exploits equilibrium or quasi-equilibrium processes to produce inert materials. In contrast, living systems depend on far-from-equilibrium kinetic processes that require a continuous flux of energy to persist and perform useful tasks. The Greek god Hephaestus forged metal automatons that he miraculously animated to perform the tasks of living creatures. Is something like this actually possible? Here we show that subjecting magnetic fluids suspended in an immiscible liquid to uniform, multidimensional, time-dependent magnetic fields, generates a variety of life-like collective dynamics, including various forms of locomotion, swarming and feeding, that are sustained by the continuous injection of energy via the applied field. These leaderless emergent behaviors occur autonomously, without human guidance, and are quite surprising. Such self-healing, remotely-powered fluid automatons could be used as an extraction/separation technology to efficiently purify water by scavenging toxic chemicals and microorganisms, or alternatively enable the controlled release of chemicals. Other possible applications include vigorous fluid mixing and even microdroplet manipulation for microfluidic bioassays.