The Polymer Society of Korea

Abstract

Colloidal photonic crystals (CPCs) embedded in soft, stretchable films offer a powerful platform for real-time optical strain sensing. We present an image-based quantification method that maps RGB data to HSV space, isolating hue as a precise, scalable indicator of mechanical deformation. As hue corresponds to the dominant Bragg-diffracted wavelength, its shift reflects nanoscale lattice changes under strain. Importantly, the hue–wavelength relationship is material-specific due to variations in refractive index, offering a unique optical fingerprint for each CPC film. Across three materials, we observe highly linear and consistent hue–strain trends. Statistical filtering and brightness normalization further ensure robustness under real-world imaging. This low-cost, non-contact approach establishes hue as a tunable mechanochromic signal, enabling next-generation applications in wearable electronics, soft robotics, and structural diagnostics.