Humidity sensor using carboxymethyl cellulose hydrogel membrane

Sensitivity and reliability of humidity sensors depend on the design of electrical components and the characteristics of materials used as absorbing layer. Here, an experiment is conducted to study the fabrication of a carboxymethyl cellulose (CMC) hydrogel membrane and its function as an absorbing layer in a resistive-based humidity sensor. The hydrogel membrane is prepared by coating the electrodes with 2 wt% CMC solution (in 3:1 water:ethanol mixture). Next, the CMC membrane is cross-linked in epichlorohydrin (ECH). Finally, the sensor is tested by measuring the resistance of the CMC hydrogel membrane at various relative humidity: RH = 53 %, 75 %, 84 % and 93 %. The measurement results show that the resistive-based humidity sensor made from the CMC hydrogel can function within this high humidity range.