Transparent and Breathable Ion Gel‐Based Sensors toward Multimodal Sensing Ability

Abstract Polymer thin‐film sensors have attracted considerable attention in various applications owing to their highly transparent, flexible, and gas‐permeable features. However, conventional thin‐film sensors based on nanomaterials suffer from poor selectivity in sensing targets and scalability of functions. Therefore, a new approach is required for achieving higher selectivity with simple processibility. This study proposes highly transparent, ultra‐flexible, and gas‐permeable polymer thin‐film sensors using ion gels as the sensing material; the sensors demonstrated the capacity for selective detections. Particularly, this study demonstrates simultaneous and independent sensing of temperature and humidity as a proof of concept. The sensors are fabricated using a simple spray coating method on a thin silicone rubber film (≈25 µm thickness). Owing to their thin‐film shape, the sensors exhibit more than 80% visible light transmittance and a higher gas permeability than the human transepidermal water loss. The temperature and humidity are simultaneously detected with a high sensitivity of 15.4% °C^–1 and 2.0% per percentage of the relative humidity, respectively, using gels containing two different ionic liquids (ILs). The results suggest that the easily modifiable nature of ILs enables the fabrication of ultra‐flexible and transparent sensors that can detect various objects using a simple method.