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3-D Printed Swimming Microtori for Cargo Transport and Flow Manipulation

Through billions of years of evolution, microorganisms mastered unique swimming behaviors to thrive in complex fluid environments. Limitations in nanofabrication have thus far hindered the ability to design and program synthetic swimmers with the same abilities. Here we encode multi-behavioral responses in artificial swimmers such as microscopic, self-propelled tori using nanoscale 3D printing. We show experimentally and theoretically that the tori continuously transition between two primary swimming modes in response to a magnetic field. The tori also manipulate and transport other artificial swimmers, bimetallic nanorods, as well as passive colloidal particles. In the first behavioral mode, the tori accumulate and transport nanorods; in the second mode, nanorods align along the tori's self-generated streamlines. Our results indicate that such shape-programmed microswimmers have the potential to manipulate biological active matter, e.g. bacteria or cells.