Chad Ropp1 Nicolas Bachelard1 Yuan Wang1 Xiang Zhang1

1, University of California, Berkeley, Berkeley, California, United States

Crystal structures are important in many fields of material science, however, such structures often exhibit inflexible order. Future technologies will require the creation of smart-materials that can change their properties on demand and exhibit multi-functional responses. Recent research has shown that order can emerge in structures that are maintained far-from-thermodynamic equilibrium through a process of self-organization. Self-organization is frequently observed in living systems, with artificially self-organized structures also displaying life-like behavior, such as with the abilities to self-heal with damage and adapt with their surroundings. In this talk, I will report a new form of non-equilibrium material that is characterized by robust pseudo-crystalline ordering. This order is sparsely periodic, with integer spacings between neighboring elements. Here, the particle-particle interactions that underlie collective ordering are mediated by wave scattering, which is externally tunable by varying the wavelength of a coherent drive. The sparse ordering allows our system to be exceedingly robust to both large mechanical perturbations and a changing environment. Compared to hydrodynamic interactions, which lead to a compact periodic order, wave-scatting provides our system with many different steady-state geometries that can be dynamically switched and reconfigured.