2024

Immonen Antti; Goel Priyanka; Koskinen Tomi; Pekkanen Matias; Kärkkäinen Tommi; Peltonen Heikki; Kuisma Mikko; Silventoinen Pertti; Tittonen Ilkka

A vital role of the human circulatory system is to distribute the metabolic heat between the body core and the peripheral parts. These thermal flow patterns can reveal important information about the bodily processes behind the observed skin surface heat flow signature. This can then be interpreted and inferred into insights about metabolism, vascular health or processes of thermoregulation.Our solution builds upon using a wearable temperature distribution sensor. The actual measurement is based on an ALD thermoelectric thin film in which the selected materials are safe for the human body contact and conform with the curvatures of the human body, enabling a proper contact. In contrast with conventional single-point measurements of wearables, the thin film enables mapping of the temperature distribution. Further, the thin film can be tailored quite freely in size. Interestingly, thermoelectricity enables transduction of electric signal directly from the temperature difference without necessarily having to be externally powered. The technological challenges to be discussed are related to measurement of thermal gradients in the film to form a two-dimensional thermal map, formation of electric contacts with the thin film and an improvement of the overall signal-to-noise ratio. Thermal information can be recorded with a high spatiotemporal resolution to gain heightened context-awareness and of the measurement conditions and heat transfer. Based on the skin sur- face measurements, subcutaneous temperatures can be estimated more reliably than conventional wearables. The proposed measurement platform enables differentiation of physiological processes such as endothelial function and improved signal robustness against the unpredictable dynamics of environmental coupling which have traditionally made continuous wrist-based temperature mea- surement practically infeasible or unreliable.