Inkjet-Printed Flexible, Sensitive Humidity Sensor with High Breathability on Electrospun Nanofibrous Mats

Inkjet printing technology has been playing an increasingly important role in manufacturing of electronic devices due to its low cost, high deposition accuracy, and mass manufacturability. Inkjet-printed flexible sensors are increasingly used in the field of flexible/wearable electronics. In this study, a kneadable humidity sensor with high breathability was developed on electrospun thermoplastic polyurethane (TPU) nanofibrous mats using inkjet printing technology. This humidity sensor shows good sensitivity over a wide humidity range, with a resistance change of only 6.13% after 1000 mechanical bends at 75% relative humidity (RH). It also has good reversibility, and the morphology and structure are not damaged upon direct contact with water droplets. In addition, the humidity sensor with good air permeability (28.8 mm s⁻¹) can be used for breath monitoring, particularly for person in sadness, panic, and tensed situations.