Measurement of Core Body Temperature Using Graphene-Inked Infrared Thermopile Sensor

Abstract

Continuous and reliable measurements of core body temperature (CBT) are vital for studies on human thermoregulation. Because tympanic membrane directly reflects the temperature of the carotid artery, it is an accurate and non-invasive method to record CBT. However, commercial tympanic thermometers lack portability and continuous measurements. In this study, graphene inks were utilized to increase the accuracy of the temperature measurements from the ear by coating graphene platelets on the lens of an infrared thermopile sensor. The proposed ear-based device was designed by investigating ear canal geometry and developed with 3D printing technology using the Computer-Aided Design (CAD) Software, SolidWorks 2016. It employs an Arduino Pro Mini and a Bluetooth module. The proposed system runs with a 3.7 V, 850 mAh rechargeable lithium-polymer battery that allows long-term, continuous monitoring. Raw data are continuously and wirelessly plotted on a mobile phone app. The test was performed on 10 subjects under resting and exercising in a total period of 25 min. Achieved results were compared with the commercially available Braun Thermoscan, Original Thermopile, and Cosinuss One ear thermometers. It is also comprehended that such system will be useful in personalized medicine as wearable in-ear device with wireless connectivity.

Hearables: New Perspectives and Pitfalls of In-Ear Devices for Physiological Monitoring. A Scoping Review

“…Given the limitations of IR thermometers, three technical studies proposed technological improvements to address the effect of anatomical and environmental factors on T measurements (Yamakoshi et al, 2010 ; Ota et al, 2017 ; Chaglla et al, 2018 ). To reduce the impact of individual ear morphology and environmental conditions, Chaglla et al ( 2018 ) proposed a graphene-inked sensor, obtained from a commercial IR thermopile and fixed by a 3D-printed hook-type enclosure. The sensing device was developed to continuously measure T from the TM and to display it on a smartphone.…”

“…Moreover, mismatch between requested standards and in-field accuracy may further explain differences among studies, which fosters further debate regarding the accuracy, validity, and reliability of in-ear measurements methods (Ring et al, 2010 ; Sund-Levander and Grodzinsky, 2013 ). Increasing the accuracy of measurements may rely on the improvement of signal/data acquisition and device stability, potentially through the implementation of new materials, as exemplified by graphene-coated T sensors (Chaglla et al, 2018 ). Probe development for T measurement should pursue personalization to adapt the device to the specific anatomy of each user (Muir et al, 2001 ; Venema et al, 2012 ; Ota et al, 2017 ), allowing a better insulation from external conditions (Teunissen et al, 2011 ; Strapazzon et al, 2015 ).…”

Evaluation of a Wearable Non-Invasive Thermometer for Monitoring Ear Canal Temperature during Physically Demanding (Outdoor) Work

“…In general, it is important to develop a continuous, non-invasive instrument that can prevent heat strain among workers and improve their health and safety while working [30][31][32]59]. In general, wearable thermometers should be suitable for all body proportions, reusable with low costs, and resistant to the effects caused by food and liquid intake [20,27,31].…”

“…Moreover, although non-invasive methods, such as ear, skin, and forehead thermometry, have become wearable, they are often impractical in work situations because they either interfere with the working conditions [27] or are unreliable at the individual level [17,22,25,28,29]. Therefore, up till now, no accurate instruments are available for continuously and non-obtrusively monitoring heat strain while performing physically demanding work [15,[30][31][32]. Therefore, there is a need for a reliable, non-invasive, continuous temperature measuring system in the form of a wearable thermometer to be able to perform real-time monitoring and prevent heat strain in physically active individuals [15,19,23].…”

Towards The Internet-of-Smart-Clothing: A Review on IoT Wearables and Garments for Creating Intelligent Connected E-Textiles

“…• Body temperature. There are different sensors that can be used to measure body temperature, like thermistors or Resistance Temperature Detectors (RTDs), although some authors suggested using other new technologies [62][63][64].…”