Design and characterization of a low thermal drift capacitive humidity sensor by inkjet-printing

作者：Rivadeneyra Almudena^*; Fernandez Salmeron Jose; Agudo Manuel; Lopez Villanueva Juan A; Fermin Capitan Vallvey Luis; Palma Alberto J

来源：Sensors and Actuators B: Chemical , 2014, 195: 123-131.

DOI：10.1016/j.snb.2013.12.117

• Moisture sensor
• Interdigitated electrode capacitor
• Flexible electronics
• RFID tag

Small, low-cost and flexible humidity sensors were designed, fabricated by using an inkjet-printing process, and fully characterized. Based on the principles of the capacitor and the ability of a polyimide to absorb humidity, the sensor was fabricated by printing silver interdigitated electrodes on a thin polyimide film of 75 pin thickness. After modeling, the total area of the printed sensor was optimized to be 11.65 mm(2). A relative humidity sensitivity of 4.5 fF/%RH and a thermal coefficient of -0.4 fF/degrees C were measured at 100 kHz, whereas the sensitivity and the thermal coefficient were 4.2 fF/%RH and -0.21 fF/degrees C, respectively, at 1 MHz. This latter result implies that it could not be necessary to include thermal compensation to use this sensor depending on the required accuracy and the chosen frequency. This work shows a reliable, fast, simple and low-cost manufacturing process to make small humidity sensors with low thermal drift and high temporal stability. These sensors could be easily integrated into inkjet-printed RFID tags for monitoring of environmental humidity in diverse applications.

• 出版日期2014-5