Cotton-Based Surfaces with Halochromic (pH-Sensitive) Properties via Anthocyanin Incorporation

In the post-COVID-19 era, there has been a growing demand for responsive, low-cost, and sustainable sensors, particularly in medical, hygiene, textile, and packaging sectors. Among the various sensor mechanisms, colour change presents unique opportunities, and pH-responsive surfaces have great potential due to their increased sensitivity and fast response. For instance, halochromic textiles offer an innovative solution for detecting bacterial growth through real-time pH monitoring. Anthocyanins (ACNs), which are natural halochromic compounds extracted from plants, are one of the best candidates for pH-sensing dyestuffs, as they can be easily incorporated into textiles and exhibit vivid colour transitions across different pH ranges. In this study, plain towel-woven cotton fabrics were dyed with varying concentrations of ACN (1, 2, 3, and 5%) to develop textiles that provide instant visual feedback to pH changes. The properties of dyestuff and cotton surfaces were analysed by SEM and FTIR. FTIR spectrum indicated that the dyestuff has hydroxyl, alkane, and aromatic groups, confirming the presence of ACN. Images and spectra also showed that ACN had been successfully incorporated into cotton fibres. Colour responses of both ACN solutions and the dyed cotton fabrics with ACN were tested in buffer solutions (pH 2-12) and bacterial solutions (pH 5-7). It was visually observed that both solutions and fabrics changed their colours at different pH values, depending on the concentration of ACN. These results suggest that ACN-dyed cotton fabrics have significant potential as pH indicators for medical and hygiene applications. This study presents a sustainable and innovative approach to sensor technologies. The novelty of this study is the direct application of ACN to commonly used plain towel-woven cotton fabrics, enabling the development of biodegradable and textile-based sensor materials. These smart fabrics offer a low-cost and environmentally friendly alternative for medical textiles and personal health monitoring products.