Stretch‐Tunable Liquid Crystal Elastomer Lasers for Visual Motion Sensing

ABSTRACT In the era of advancing mobile and wearable technologies, the evolution of lasers toward flexible deformation is becoming increasingly prominent. This study develops a novel, flexible, and stretchable cholesteric liquid crystal elastomer (CLCE) laser device. This innovative device demonstrates a unique ability to undergo rapid, progressive, and reversible color changes due to force‐induced reactions. Stretch switchable (random or bandgap lasing) and stretch wavelength tunable (560–625 nm) lasers are obtained by introducing the laser dye PM597 into the CLCE. To further extend the control spectrum of laser output wavelengths in flexible systems, this research introduces two laser dyes, namely donor dye PM597 and acceptor dye NB, validating the feasibility of a stretch‐dependent Förster resonance energy transfer flexible laser. By manipulating the stretching force to drive the movement of the CLCE bandgap, our flexible laser device dynamically shifts its lasing output from 560 to 750 nm. Leveraging the CLCE's exceptional mechano‐chromic and mechanical properties, a visual interactive device for real‐time monitoring of human joint movements is designed. This flexible CLCE, as an elastic functional soft material, holds significant promise for applications in smart wearables, soft robotics, and human‐machine interfaces.