A Background-Independent Structural Colored Gel Based on Cellulose/PEDOT: PSS for Highly Sensitive Dual-Mode Sensing

Hydroxypropyl cellulose (HPC) spontaneously self-assembles into a cholesteric liquid crystal (CLC) structure at certain concentrations in aqueous solution, exhibiting vivid structural colors. Due to incoherent scattering, the apparent color of translucent HPC CLCs is often diminished and nearly invisible against white or colored backgrounds. In this work, a cellulose-based mixture with structural coloration and conductivity was engineered by integrating poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) into HPC. The incorporated conductive dark PEDOT: PSS suppresses the effect of incoherent scattering and reduces background-color interference, enabling background-independent structural color. This approach empowers the structural coloration independent of backgrounds and imparts conductivity to the mixture. Leveraging these intriguing properties, the UV-crosslinked HPC-PEDOT: PSS-PEGDA400 gel possesses exceptional sensitivity with a gauge factor of 15.30, combined with a synchronous mechanochromic response. Significantly, the cellulose-based gel is endowed with not only durable and reversible mechanochromic but also electromechanical responses to stimuli such as stretching and finger-bending. The first feature enables intuitive user-visible interactions and supports advanced inflatable displays, while the second feature facilitates the quantitative assessment of mechanical deformation. This work achieves the dual-modal functionalities in a single gel, offering insights into next-generation structural colored materials for multifunctional electronic skins and dynamic displays.