A Carbon Black/Polyvinyl Alcohol-Based Composite Thin Film Sensor Integrating Strain and Humidity Sensing Using the Droplet Deposition Method

Carbon black (CB) is a low-cost and excellent conductive material, and polyvinyl alcohol (PVA) is a non-conductive material with the advantages of easy processing and high mechanical stability. Here, we report a CB/PVA-based flexible conductive polymer film suitable for small strain detection and humidity detection. Thin film is formed by depositing the CB/PVA dispersion liquid droplets on a cleaned silicon/silicon dioxide (Si/SiO2) substrate. Theoretically, CB/PVA films can be transferred or formed on other substrates, such as polydimethylsiloxane, which have the advantage of flexibility. The droplet deposition method not only enhances the controllability of the film thickness and wastage of materials, but also improves the sensitivity of the prepared film. The electrical conductivity of the CB/PVA composite film and the relationship between the resistance change and strain were measured by the four-point bending method, which showed a good gauge factor of 30 when the strain rate was 0.007%. In addition, the sensor also showed excellent sensing performance and repeatability at humidity levels ranging from 10% to 70% RH. These results demonstrate that the CB/PVA thin film prepared in this work has the advantages of a simple fabrication process, low-cost, multifunctional properties, and high device sensitivity, providing further insights for detecting minor strain and humidity.