Liquid crystals enable chemoresponsive reconfigurable colloidal self-assembly.

Abstract

Liquid crystals (LCs) and colloids have large response functions, a property that Nobel laureate Pierre-Gilles de Gennes (1) identified as the most significant unifying concept of soft matter. This strong response to external fields enables practical applications ranging from nonmechanical beam steering, to information displays, to label-free biological sensors (2–4). Poulin et al. (5) have demonstrated that colloidal particles embedded in a nematic solvent are stabilized by topological defects and interact via a new type of interactions that arise from the LC’s orientational elasticity. This seminal work initiated a great deal of excitement, and many self-assembled colloidal architectures have been reported in the bulk and at surfaces of LCs (6–14), promising a new class of reconfigurable composites that may enable mass production of tunable photonic crystals and optical metamaterials (14, 15). LC solvents can provide conceptually new means of predesigned control over self-organization of micrometer- and nanometer-sized particles that are not accessible in isotropic hosts. However, experimental demonstrations of such robust control are scarce and usually limited to the use of laser beams, electric fields, and colloidal particle shapes (6, 10–14). The study by Koenig et al. (16) in PNAS is a breakthrough in realizing a robust chemical control of colloidal self-assembly at the interface between an isotropic fluid (i.e., water) and LCs.