Construction and Performance of a Nanocellulose–Graphene-Based Humidity Sensor with a Fast Response and Excellent Stability
Li Gong, Hao Fu, Lin Liu, Zhen Li, Jianqiang Guo, Zheng Cao, Juming Yao
Abstract
Humidity sensors have been widely applied in environmental monitoring, respiratory monitoring, electronic skin, noncontact switch, etc. However, weak interface interactions between a flexible substrate and conductive fillers will deteriorate the sensing performance. Herein, a flexible, rapid-response, and durable humidity sensor was proposed via employing cellulose nanofiber (CNF)-dispersed graphene (Gr) as a humidity sensing layer, which could be easily filtered onto a coessential CNF film (CNFF) to form the humidity sensor. CNFs as a dispersant and bonder strengthened the adhesion of graphene on the surface of the CNFF substrate. Simultaneously, CNFs as a reservoir provided abundant adsorption sites to capture water molecules and promoted electron transfer from adsorbed water molecules to graphene, further amplifying electrical signals by a hygroscopic expansion of the sensing layer under humidity conditions. Benefiting from this unique composition and structure, the prepared humidity sensor exhibited a rapid response (45 s) and recovery time (33 s), low hysteresis (4%), wide RH detection range (15–99%), and long-term stability (15 days). Further, the sensor could monitor the humidity of human skin and human breath, indicating a versatile noncontact humidity sensing function by altering its component proportion of CNF-to-Gr on demand.