High-Sensitivity Colorimetric Sensor Based on Fabry–Perot Cavity for Humidity Detection

In the field of environmental monitoring, sensors that can quickly and accurately detect humidity play a key role. Traditional resistive and capacitive humidity sensors are difficult to obtain accurate humidity information due to the complexity of internal data conversion and the high precision of design. Inspired by the responsive coloring characteristics of longicorn beetles in different humidity environments, the research team proposed a novel humidity colorimetric sensor based on Fabry-Perot (F-P) optical structure. The structure of the sensor consists of three parts: “reflective layer, humidity sensitive, and expandable interference cavity and reflective layer.” When the external humidity changes, the interference cavity will expand regularly under the influence of water molecules, so that the structural reflection curve of the sensor appears resonance red shift phenomenon and then presents different colors corresponding to the ambient humidity. Compared with traditional sensors, this simple colorimetric sensor has significant advantages. Its measurement range can be as high as 80%, and the recovery speed is also very fast, only 100 ms. The researchers also built a portable and easy-to-operate sensing system to realize colorimetric analysis based on smart phones. In addition, the structural substrate of the sensor is made of flexible materials. Based on this feature, it can also be applied to the field of camouflage clothing, allowing clothing to adaptively change color in humid and dry environments, with both practical and decorative functions. This bionic visual humidity sensor is expected to be widely used in many fields, such as real-time environmental monitoring and intelligent wearing, showing great application potential.