Low-power Smart Earring for Longitudinal Earlobe Temperature Sensing

Abstract

Body temperature is an important vital sign which can provide valuable insights into a person's health condition, including the presence of fever. Moreover, it is known to be correlated with activities such as eating, exercise, and mental states. However, continuous temperature monitoring poses a significant challenge. This thesis presents Thermal Earring, a first-of-its-kind smart earring that enables a reliable non-invasive wearable solution for continuous temperature monitoring. The Thermal Earring takes advantage of the unique position of earrings in proximity to the head, a region with tight coupling to the body unlike watches and other wearables which are more loosely worn on extremities. We develop a hardware prototype in the form factor of real earrings measuring 11.3 mm, weighing 335 mg, and consuming only 14.4 uW which enables a battery life of 28 days in real-world tests. We demonstrate this form factor is small and light enough to integrate into real jewelry with fashionable designs. Additionally, we develop a dual sensor design to differentiate human body temperature change from environmental changes. We explore the use of this novel sensing platform and find it measures temperatures that are stable within ±0.32°C during periods of rest. Using these promising results, we investigate its capability of detecting fever by gathering data from 5 febrile patients and 20 healthy participants. Further, we perform the first-ever investigation of the relationship between earlobe temperature and a variety of daily activities, demonstrating earlobe temperature changes related to eating and exercise. We also find the surprising result that acute stressors such as public speaking, exams, and paper deadlines cause measurable changes in earlobe temperature. We perform multi-day in-the-wild experiments and confirm the temperature changes caused by these daily activities in natural daily scenarios. This initial exploration seeks to provide a foundation for future fever monitoring, activity detection, and stress assessment.