Natural anthocyanin-based wearable colorimetric pH indicator with high color fastness

Smart textiles with real-time visual monitoring abilities of environmental pH hold significant importance in wearable products. Natural dyes have gained growing interest as eco-friendly pH indicators, however, their stability and large-scale isolation remain challenging. In this work, we developed a type of pH-monitoring colorimetric indicator based on anthocyanins, a natural dye extracted from red cabbage, with enhanced affinity to cotton fiber substrates by utilizing metal salts and biopolymers. Compared to cotton fabric directly dyed with pristine anthocyanins, this colorimetric fabric demonstrates higher color contrast, superior reversibility of color change, and enhanced light and washing color fastness. The color strength (K/S) was significantly improved from 0.136 for untreated fabric to 1.266 for colorimetric fabric, and the excellent colorimetric properties maintained either after over 20 h washing or 12 h exposure to sunlight. This work addressed the issue of the easy light degradation of biomaterials, and provided a feasible optimization strategy for the development and application of environment-responsive biomass colorimetric textiles as smart and wearable products.