Odd dynamics of living chiral crystal

Many organisms, from single-cell to multicellular ones, form colonies through collective behavior for communal effects. In this work, we discovered the phenomenon of hydrodynamics self-assembly of sea star embryos during their early development. Embryos form a stable bound state at the water-air interface and hydrodynamically self-assemble into 2D crystals with hexagonal order. Combining experiments, hydrodynamic theory, and simulations, we demonstrate that the formation, dynamics, and dissolution of these living crystals are controlled by the natural development of the embryos. Remarkably, the living chiral crystals exhibit self-sustained oscillations with dynamic signatures recently predicted to appear in odd elastic materials, a novel mechanical material property. See here for general perspective. More generally, our work demonstrates how autonomous morphological development at the single-organism level can control collective dynamics and symmetry breaking at the macroscale.

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This system opens up a lot of opportunities to investigate odd dynamics in chiral active matter. Can we fluidize the system by tuning viscosity of the medium? Does the system exhibit hexatic phase during fluidization? What is the role of disorder in self-assembly process of chiral active matter? Beyond sea star embryos, many marine invertebrates larvae have shown the capacity to self-assemble into a living chiral crystal. Our lab is interested in using Platynereis embryo to build new chiral crystal. Due to its phototactic ability, this system offers us the possibility of modulating chiral crystal dynamics using light.