(379g) Programming Shape and Motion into Active Loops

Recent years have witnessed the growth of nano and micron scale robotic mechanisms using physicochemical principles of DNA, stimuli-responsive polymers and MEMS. We add active matter to this toolkit motivated by the development in this field that has equipped us with a wide variety of organic and inorganic materials that can harness environmental energy into a propulsion force in a tunable and robust fashion. In this work, we design and investigate a system where arbitrary shape can be programmed into loops of active particles. The shape and motion information is encoded in the arrangement of active force direction and magnitude along the loop. When actuated, the loops fold into programmed shapes while the internal space is available to accommodate additional components such as sensors, controller, chemicals, and communication devices. The shapes are composed of straight and/or bent segments of the loop connecting at sharp corners, giving shapes a characteristic zigzag feature. We use numerical and analytical methods to investigate the model system. We also discuss design heuristics to program a variety of shape features into loops and build complex shapes that avoid metastable traps during self-assembly. Applications of our work include non-invasive medical robotics using programmable loops, ensemble of loops self-organizing into novel structures, and bottom-up fabrication of micron sized machine parts.