Dynamic self-assembly of microscale rotors and swimmers

Self-assembly is a process found throughout nature and is often dynamic, requiring fuel to occur. Artificial examples are valuable both as aids to understanding biological systems and for developing manufacturing techniques for micron-scale machines. We will describe the behaviour of micron-scale rods, constructed of three equal length segments of gold, platinum and gold (Au-Pt-Au). When placed in a solution of hydrogen peroxide fuel, these are expected to create an extensile-like flow in the surrounding fluid. These immotile rods self-assemble into structures that exhibit the two fundamental types of motion: rotation and translation, in the form of steadily rotating stacks and T-shaped swimmers. This is a rare example of an artificial system where dynamic and reversible self-assembly results in ordered structures which exhibit emergent motility.