A flexible humidity sensor based on silk fabrics for human respiration monitoring

Development of flexible devices for continuous respiration monitoring has been fueled up recently due to their great importance in constructing wearable healthcare systems. However, there is no report on silk fabric-based devices for precise detection of the human respiratory rate and depth. In this work, a silk fabric-based respiration sensor was fabricated by successive electroless plating of conductive interdigital electrodes and spray-coating of a graphene oxide (GO) sensing layer. Surface morphologies of the devices were characterized to show the construction of the sensor. The uniform surface distribution of GO nanosheets was analysed using the Raman mapping method. After optimization, the as-prepared device could accurately detect the human respiration rate and effectively differentiate normal, deep and fast breathing. The flexibility test indicates that the sensor can tolerate 2500 repetitions of bending and twisting without influencing its performance. Moreover, by designing a spray-coating mask, GO layers with various patterns could be deposited to achieve both functionality and aesthetics. This work not only develops a silk fabric-based sensor for potential application in assessing the basic human health-status, but also provides a facile approach to preparing textile-based wearable electronic devices.