Programmable Design and Performance of Modular Magnetic Microswimmers.

Synthetic biomimetic microswimmers are promising agents for in vivo healthcare and important frameworks to advance the understanding of locomotion strategies and collective motion at the microscopic scale. Nevertheless, constructing these devices with design flexibility and in large numbers remains a challenge. Here, a step toward meeting this challenge is taken by assembling such swimmers via the programmed shape and arrangement of superparamagnetic micromodules. The method's capacity for design flexibility is demonstrated through the assembly of a variety of swimmer architectures. On their actuation, strokes characterized by a balance of viscous and magnetic forces are found in all cases, but swimmers formed from a series of size-graded triangular modules swim quicker than more traditional designs comprising a circular "head" and a slender tail. Linking performance to design, rules are extracted informing the construction of a second-generation swimmer with a short tail and an elongated head optimized for speed. Its fast locomotion is attributed to a stroke that better breaks beating symmetry and an ability to beat fully with flex at high frequencies. Finally, production at scale is demonstrated through the assembly and swimming of a flock of the triangle-based architectures to reveal four types of swimmer couplings.