Highly Sensitive Interdigitated Capacitive Humidity Sensors Based on Sponge-Like Nanoporous PVDF/LiCl Composite for Real-Time Monitoring

In this study, a sponge-like poly(vinylidene fluoride) (PVDF)/lithium chloride (LiCl) nanocomposite-entrenched interdigitated capacitive (IDC) sensor was developed for real-time humidity-sensing applications. Here, we demonstrated a sponge-like nanoporous structure ranging from 200 nm to 2 μm size holes, the PVDF/LiCl structure fabricated on an interdigitated capacitor (IDC) electrode functioning as a high-performance sensor because of the presence of ionized LiCl. The nanoporous PVDF/LiCl composite-based humidity sensor exhibited a high sensitivity of 12.6 nF/% relative humidity (RH), a linearity of 0.990, and a low hysteresis of 2.6% in the range of 25-95% RH. The composite film exhibited a response time of 17.7 s, a recovery time of 21 s, and an intensified increase of 8.02 nF/s (a decrease of 6.7 nF/s). The sensor designed demonstrates ultra-high sensing characteristics with 10 times higher sensitivity, i.e., 12.678.96 pF/%RH as compared to other polymer-based composite humidity sensors. Owing to the sensing performance and portability, the proposed nanoporous PVDF/LiCl composite-based IDC sensor is expected to be a promising platform for a wide range of humidity-sensing applications, including real-time breath monitoring and non-contact sensing.