Active Colloidal Molecules with Dynamic Configurational Freedom.

Molecular machines and microorganisms employ dynamic shape changes to enable adaptive function. In contrast, active colloidal machines and micromotors, their synthetic counterparts, are typically preconfigured and mechanically rigid, which limits the range of their dynamic behavior and thereby their functionality. Here, through physical interactions alone, we assemble active colloidal molecules with flexible configurations that evolve freely and continuously in time. Unlike existing colloidal systems that either offer structural flexibility in passively diffusing assemblies, or impose fixed configurations in self-propelling ones, our colloidal molecules both dynamically self-assemble and disassemble on demand and directly propel themselves through their own internal restructuring. This, in turn, bestows enhanced self-regulation, self-steering, and avoiding capabilities upon encountering other molecules. These capabilities suppress clustering and motility-induced phase separation, allowing them to remain dispersed, well-separated, and still actively moving even at high concentrations. Micromotors with dynamic configurational freedom thus constitute a step toward autonomous motion beyond classical synthetic active matter, and allow for designing "intelligent" microrobots and responsive functional active materials at the nano- and microscale.