Humidity /temperature/ pH multi-responsive fabric-based colorimetric sensor for detection and information encryption

Relative humidity (RH), temperature, and pH as important environmental parameters that are closely related to industry, agriculture, and people's life. Therefore, the development of a colorimetric sensor that can monitor the RH, temperature, and pH in real-time is highly desired. In this work, a fabric-based flexible colorimetric sensor is easily manufactured by screen printing the mixture of cresol red (CR), thymol blue (TB) and boric acid (H3BO3) on the fabric. Compared with the traditional single stimulus colorimetric sensor, this fabric device can respond to multiple stimulus factors including humidity, temperature, or pH. The simple coating treatment can endow the colorimetric sensor with fast response without compromising its flexibility. Exposed to different stimulus conditions, the colorimetric sensor has a unique color change effect, such as humidity-responsive pink-yellow, temperature-responsive yellow-pink, and pH-responsive pink-purple. The flexibility and versatility of the fabric sensors are showcased with the applications in temperature/humidity/pH detection, cultural relics protection and information encryption. We believe the colorimetric sensor would have potential in environmental monitoring, health care, encrypted information patterns, and intelligent wearables, etc.