Stretchable Cellulosic Cholesteric Liquid Crystal Filaments with Color Response

Abstract

Utilizing soft optical materials in mechanochromic sensing is an intriguing concept with several application areas in soft robotics and functional wearables. Herein, we developed stretchable cholesteric cellulosic liquid crystal filaments by simply encapsulating the aqueous hydroxypropyl cellulose (HPC) mesophases in a sealed thermoplastic elastomeric tubing. The tubular confinement of the HPC induced a well-defined cholesteric structure in which the quasi-layers are concentrically distributed along the fiber axis. The flow properties of the aqueous HPC showcased the ability to mimic the stretching and relaxing behavior of the elastomeric tubing, resulting in a spontaneous color change in response to mechanical deformation. This soft optical system can act as a stretchable colorimetric sensor for both tensile and compression forces enabled by the uniform alignment and dynamic deformation of the HPC mesophase.