Nematic colloidal micro-robots as physically intelligent systems

TL;DR

This paper introduces nematic colloidal micro-robots that utilize the elastic and topological properties of nematic liquid crystals to enable dynamic, reconfigurable cargo manipulation and assembly, advancing physically intelligent micro-robotic systems.

Contribution

Design and fabrication of a 4-armed ferromagnetic micro-robot that embeds and reconfigures information in nematic director fields for complex cargo manipulation.

Findings

Micro-robots can manipulate cargo via nemato-elastic interactions.

Rotating micro-robots dynamically reconfigure the energy landscape.

Topological defect dynamics enable programmable transient information.

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 like nematic liquid crystals (NLCs) provide untapped opportunities to embed interactions via their topological defects, complex elastic responses, and their ability to dramatically restructure in dynamic settings. Here we design and fabricate a 4-armed ferromagnetic micro-robot 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 for top-down cargo manipulation. We demonstrate robust micro-robotic manipulation strategies 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.