Cellulose-Based Stimuli-Responsive Anisotropic Hydrogel for Sensor Applications

Hydroxypropyl cellulose (HPC) is a hydroxypropylated derivative of cellulose with a lyotropic liquid crystal (LC) property and thermochromism. We introduced HPC into poly 2-acrylamido-2-methylpropane sulfonic acid (PAMPS), forming an anisotropic hydrogel by mechanical shearing. The polymerized long-range ordered HPC/PAMPS hydrogel shows a uniform interference color between crossed polarizers, which could be applied as a multifunctional sensor responding to temperature, pressure, and tensile force. In particular, the oriented HPC/PAMPS hydrogel, as a temperature sensor, can respond to a wide temperature range, and the vivid interference color change has little transmittance loss due to the confinement of a hydrogel network. This work may broaden the application areas of the anisotropic hydrogel and present inspirations into the multi-functional cellulose-based hydrogel sensors.