Nematic Colloidal Micro-Robots as Physically Intelligent Systems

Abstract

Physically intelligent micro-robotic systems exploit information embedded in micro-robots, their colloidal cargo, and their milieu to interact, assemble, and form functional structures. Nonlinear anisotropic fluids such as nematic liquid crystals (NLCs) provide untapped opportunities to embed interactions via their topological defects, complex elastic responses, and ability to dramatically restructure in dynamic settings. Here a four-armed ferromagnetic micro-robot is designed and fabricated to embed and dynamically reconfigure information in the nematic director field, generating a suite of physical interactions for cargo manipulation. The micro-robot shape and surface chemistry are designed to generate a nemato-elastic energy landscape in the domain that defines multiple modes of emergent, bottom-up interactions with passive colloids. Micro-robot rotation expands the ability to sculpt interactions; the energy landscape around a rotating micro-robot is dynamically reconfigured by complex far-from-equilibrium dynamics of the micro-robot's companion topological defect. These defect dynamics allow transient information to be programmed into the domain and exploited. Robust micro-robotic manipulation strategies are demonstrated that exploit these diverse modes of nemato-elastic interaction to achieve cargo docking, transport, release, and assembly of complex reconfigurable structures at multi-stable sites. Such structures are of great interest to future developments of LC-based advanced optical device and micro-manufacturing in anisotropic environments.