Wide range high speed relative humidity sensor based on PEDOT:PSS–PVA composite on an IDT printed on piezoelectric substrate

• Published in: Sensors and actuators. A. Physical. Vol. 228; pp. 40 - 49
• Main Authors: Choi, Kyung Hyun, Sajid, Memoon, Aziz, Shahid, Yang, Bong-Su
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.06.2015
• Subjects: Aqueous solutions; Capacitance; Detection; Humidity; Impedance; PEDOT:PSS; Piezoelectric; Piezoelectricity; Polyvinyl alcohols; PVA; Response time; SAW; Sensors; SAW; PVA; Response time; Piezoelectric; Humidity; PEDOT:PSS
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2015.03.003

•Conducting/insulating (PEDOT:PSS/PVA) polymer blend is used for humidity sensing for the first time.•Effect of increasing conductivity on sensor response in terms of range, sensitivity and response time has been investigated.•Response time, measurement range and sensitivity are found to be excellent.•High precision IDT on piezo-electric substrate produces SAW effect and improves efficiency and accuracy of sensor.•The sensor can work in both resistive and capacitive modes. A high performance humidity sensor for environmental and health monitoring was fabricated with a polymer–polymer composite sensing layer. PEDOT:PSS/PVA composite was synthesized by physically mixing PEDOT:PSS aqueous solution with PVA aqueous solution and was then sonicated and stirred at elevated temperatures. Sensors were fabricated by depositing the sensing layer on an IDT printed on a piezoelectric substrate. The sensors’ electrical characterizations were performed to find out the response toward varying humidity levels. The results showed that the composite's response toward humidity change is very stable and can effectively measure low humidity levels with fast response time. The AC capacitance and impedance of the sensor were measured between 0%RH and 80%RH. The maximum change in impedance was from 137kΩ to 110kΩ and for capacitance from 96pF to 124pF. The sensors were deployed in a real time humidity measurement and the readings were converted into corresponding %RH. The results indicated that the sensors show promising response with ±1% reading error. The response and recovery times of the sensor were measured to be 0.625s and 0.53s respectively showing excellent performance of the sensor toward increasing and decreasing humidity levels.