A Wearable Supramolecular Fingertip Sensor for Colorimetric Detection of Food-Derived Tyramine.

Wearable sensing technologies are emerging as promising tools for rapid on-site screening and process monitoring, owing to their direct and user-friendly human-device interfaces. However, achieving rapid, selective, and visually interpretable early warning detection in wearable formats remains challenging. Here, we propose a fingertip-compatible supramolecular colorimetric platform based on an indicator displacement assay (IDA) for the rapid detection of tyramine (TA), a representative biogenic amine in fermented foods. A pH-responsive dye precomplexed with 4-sulfonic calix[6]arene (Dye@SC6) was immobilized within hydrophilic microdomains on POTS-TiO2-modified hydrophobic paper; strong capillary anchoring confined the sample droplet within these microreactors and inhibited lateral diffusion. Upon TA exposure, SC6 preferentially binds to amines, displacing the dye and inducing a local pH increase, which drives dye deprotonation and leads to a significant colorimetric shift. Smartphone-extracted RGB analysis showed a linear relationship between R/G and TA concentration in the range of 4.10-16 mM (R2 = 0.9970), with a detection limit of 1.23 mM. Furthermore, K-nearest neighbor (K-NN) classification achieved accuracies of 98.9% (R/G) and 100% (G/B). Integrated into a glove fingertip, this platform enables a rapid, reagent-efficient, and field-deployable "touch-to-detect" wearable sensing workflow.