Graphene/polypyrrole/carbon black nanocomposite material ink-based screen-printed low-cost, flexible humidity sensor

Abstract The detection of humidity is crucial for various applications in industry, healthcare, and the environment. To meet the needs of many of these applications, humidity sensors must be flexible, disposable, and easily fabricated. This article introduces a cost-effective and flexible humidity sensor created on a paper substrate, using graphene-polypyrrole-carbon black ink. The sensor shows excellent sensing capabilities, with a resistance change of approximately 12.2 Ω/%RH when exposed to humidity ranging from 23%RH to 92.7%RH. Additionally, the sensor is highly flexible, stable, and repeatable for over 50 cycles, with a short response/recovery time of approximately 5 s/7 s for respiration rate monitoring. Furthermore, the sensor demonstrates good reproducibility, with minor variations of approximately ± 1 Ω/%RH. The performance of the produced humidity sensor is assessed for monitoring humidity in a spatial setting as well as monitoring soil moisture. As a result, these findings indicate that the proposed humidity sensor is resilient enough to be used in wearable and flexible electronic devices.