Inkjet-Printed Human Body Temperature Sensor for Wearable Electronics

Abstract

This paper presents an all-printed human body temperature sensor developed on a plastic substrate with high deformation characteristics. The sensors are developed on <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50~\mu \text{m}$ </tex-math></inline-formula> thick Kapton substrate with structural configuration of silver interdigital electrodes (IDEs) fabricated through inkjet material printer DMP 2850 and the sensing film based on carbon black deposited through doctor blade coating. Interdigital distance of the IDEs were optimized by evaluating sensors’ performance against changing the fingers spacing within a close range of 0.1–1 mm. Good sensitivity i.e. 0.00375 °C <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> is achieved at a temperature range of 28 to 50 °C with response and recovery times of 4 and 8.5 sec, respectively. Robustness of the sensor was also evaluated for a period of 50 days and a negligible drift ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\Omega$ </tex-math></inline-formula> ) in the base resistance was recorded. The sensor exhibited bendability down to 5 mm and was also characterized for the chemical and electrical properties i.e. resistance variation, surface morphology and Raman shift analysis of the carbon black. This wearable sensor can potentially be applied on human body for continuous temperature monitoring as well as on the artificial skin for social and industrial robotic applications.