Highly Sensitive Flexible Humidity Sensor Based on Bacterial Cellulose/MXene/Graphene Oxide Composite Film

The two-dimensional (2D) MXene is a promising material for humidity sensors due to its large specific surface area and high electrical conductivity. However, the limitation of its layer spacing makes it difficult to realize highly sensitive humidity sensors. Here, highly sensitive flexible humidity sensors were developed by using the composite film of bacterial cellulose (BC)/MXene/graphene oxide (GO), in which BC was used to construct the network structure for attaching MXene, while GO was used to enhance its hygroscopicity. As a result, the prepared humidity sensors based on BC/MXene/GO composite had the responsivity of up to 217%, response time of 24.2 s, wide measurement range (11 to 98% RH), and good repeatability. The humidity sensing mechanisms were attributed to the swelling effect and the Grotthuss chain reaction, depending on the content of GO in the BC/MXene/GO composite. The prepared humidity sensors based on BC/MXene/GO composite were applied for respiratory monitoring and finger noncontact switches. These findings contribute to the rapid development of flexible humidity sensors based on MXene and related 2D materials.