Tzer Han Tan, Assistant Professor, Department of Physics, UC San Diego

Nonreciprocity in biological and synthetic active matter gives rise to distinctive material properties, such as odd material moduli, sustained wave propagation, and transverse responses. In this talk, I will first highlight the odd elastodynamics that emerge in a living chiral crystals composed of thousands of spinning starfish embryos. Combining experiments, theory and simulations, we demonstrate that the formation, dynamics and dissolution of these living crystals are controlled by the hydrodynamic properties and the natural development of embryos. Remarkably, living chiral crystals exhibit self-sustained chiral oscillations as well as unconventional deformation response behaviors recently predicted for odd elastic materials. Building on these insights, we developed a bioinspired robotic swarm with programmable nonreciprocal interactions. Our experiments demonstrate that tuning the interaction strength can transition the system from a solid-like state with odd vibrational modes to a fluid-like regime with edge states. Strikingly, robot pairs exhibit emergent oscillatory dynamics and phase synchronization, both essential to drive odd wave propagation in many-body collectives. Together, these findings illustrate how nonreciprocity in living and robotic matter can enable nonequilibrium phases of chiral active matter with non-classical emergent properties.