A Humidity Sensing Organic-Inorganic Composite for Environmental Monitoring

Abstract

In this paper, we present the effect of varying humidity levels on the electrical parameters and the multi frequency response of the electrical parameters of an organic-inorganic composite (PEPC+NiPc+Cu2O)-based humidity sensor. Silver thin films (thickness ∼200 nm) were primarily deposited on plasma cleaned glass substrates by the physical vapor deposition (PVD) technique. A pair of rectangular silver electrodes was formed by patterning silver film through standard optical lithography technique. An active layer of organic-inorganic composite for humidity sensing was later spun coated to cover the separation between the silver electrodes. The electrical characterization of the sensor was performed as a function of relative humidity levels and frequency of the AC input signal. The sensor showed reversible changes in its capacitance with variations in humidity level. The maximum sensitivity ∼31.6 pF/%RH at 100 Hz in capacitive mode of operation has been attained. The aim of this study was to increase the sensitivity of the previously reported humidity sensors using PEPC and NiPc, which has been successfully achieved.

Design and Development for Capacitive Humidity Sensor Applications of Lead-Free Ca,Mg,Fe,Ti-Oxides-Based Electro-Ceramics with Improved Sensing Properties via Physisorption

“…The C -value increased from 3.2183 × 10 −11 F to 9.9741 × 10 −10 F with a “ S ” of ~3000% at the signal frequency of 10 2 Hz but when the test frequency is 10 5 Hz, the capacitance varied from 1.2832 × 10 −11 to 2.8174 × 10 −11 F with “ S ” of ~120% across the RH range of 33%–95%, respectively. The sensitivity of our developed sensor is higher than that of some other ceramic based humidity sensors reported elsewhere (for example, ~2900% for porous ZnAl 2 O 4 spinel nanorod, 85% for silica nanoparticles aerogel thin films, ~966% for SiC nanowires, ~800% for thermally carbonized porous silicon, ~500% for alumina nanowire, 1490% for (PEPC + NiPc + Cu 2 O) and so on based humidity sensors) [16,56,57,58,59,60]. Therefore, in our further study the 10 2 Hz would be considered as best test frequency for the analysis of sensor characteristics.…”

“…This result indicates that the hysteresis of our developed CMFTO electro-ceramic based humidity sensor is relatively lower than that of other different capacitive humidity sensors (i.e., ~4.16% for ZnO/Si-based, ~4.5% for SiC nanowire-based, ~4% for alumina nanowire-based, ~5% for graphene oxide-based, ~12% for (PEPC + NiPc + Cu 2 O)-based and so on) developed by other studies reported elsewhere [16,54,59,60,66]. The lower hysteresis value was obtained owing to the relatively faster adsorption and desorption rate of water molecules on the surface of the CMFTO electro-ceramic in comparison to the other materials [54,55].…”

Humidity Sensors Principle, Mechanism, and Fabrication Technologies: A Comprehensive Review

“…Several capacitive RH sensors have been designed and produced on interdigitated gold, platinum or silver electrodes with this platform incorporating organic polymer thin films or porous ceramics such as alumina, perovskites, and porous silicon based on printing deposition or coating techniques onto a ceramic substrate [321,322]. …”

Investigating sensing properties of poly-(dioctylfluorene) based planar sensor

“…Moreover, the properties of these materials alter drastically due to the interaction of molecules with environmental parameters such as temperature, humidity, pressure and gases. Keeping in mind the response of organic semiconductors, several humidity [3][4][5] and multifunctional [6,7] thin film sensors have been investigated.…”