Reconfigurable assembly of nematic colloids commanded by photoactivated surface patterns

TL;DR

This paper demonstrates a reversible, photo-controlled method to assemble and transport micron-sized particles in a nematic fluid, enabling customizable paths and flow control for potential applications in chemical and biological systems.

Contribution

The study introduces a novel approach combining photoactivated surface patterns with AC electrophoresis and elastic nematic modulation for reconfigurable particle transport.

Findings

Particles can be directed along arbitrary paths using UV/blue light patterns.

The method allows reversible assembly and transport of large particle ensembles.

Versatile application potential for inanimate and living materials.

Abstract

Different phoretic driving mechanisms have been proposed for the transport of solid or liquid microscopic inclusions in integrated chemical processes. However, the ability to reversibly address both the flow path, rate, and local reactant concentration has not yet been realized. Here we show that a substrate chemically modified with photosensitive self-assembled monolayers allows to directly command the assembly and transport of large ensembles of micron-size particles and drops dispersed in a thin layer of anisotropic fluid. Our strategy separates particle driving, realized via AC electrophoresis, and steering, achieved by elastic modulation of the host nematic fluid. Inclusions respond individually or in collective modes following arbitrary reconfigurable paths imprinted via UV/blue illumination. Relying solely on generic material properties, the proposed procedure is versatile enough for the development of applications involving either inanimate or living materials.