Investigating Carboxymethyl Cellulose in Aerosol Jet Printed Microwave Humidity Sensors

This study presents a passive and chipless humidity sensor to monitor relative humidity (RH) continuously. The sensor is constructed on kapton substrates, a C-shaped resonator integrated with meander line structure that operates at 5.925 GHz and is printed with silver nanoparictles (Ag NPs) conducting ink. Eco-friendly, carboxymethyl cellulose (CMC) fabricated in between conducting AgNP lines to monitor RH in slowly changing environment. Both layers are deposited using ultrasonic aerosol jet printer technology. The CMC layer served as an active sensing element, enhancing the microwave resonator’s sensitivity and overall performance in detecting humidity. The sensor demonstrates high sensitivity, reaching up to 0.77MHz/%RH across a humidity range of 47.5% to 90%.