Figure 10 (a) Proof of Concept of Dual Network Thermoelectric Hydrogel Respiratory Monitoring System with Mask Attached, Infrared Image of Wearing Mask and Monitoring Results. Reprinted with permission from ref. 19. Copyright 2022 American Chemical Society. (b) The tester wore a headband with the sensor. The next is the response of the sensor when cycling. Reprinted with permission from ref. 89. Copyright 2022 American Chemical Society. (c) Panoramic view of the gel-based thermoelectric patch for body temperature monitoring. Relationship between current and body temperature in the three typical regions. Body temperature monitoring and the corresponding temperature signal are displayed on terminals. Insets: Photographs of the gel patch that was twisted and bent (scale bar: 1 cm). Reprinted with permission from ref. 20. Copyright 2021 American Chemical Society.
The thermoelectric gel patch prepared by Zhang et al.,[19] as illustrated in Figure 10a, effectively converted physiological data into easy-to-understand electrical pulse signals by taking advantage of the temperature difference between the environment and the heat generated by human breathing. Interestingly, the gel patch functioned reliably even in temperatures below 0 °C, implying its adaptability to low-temperature environments. In another investigation, Zhang et al. developed a highly-sensitive temperature sensor using thermoplastic polyurethane fiber that can accurately monitor human activity. The sensor, with a remarkable tensile strain of up to 270%, can be conveniently worn as a headband to monitor the body temperature of athletes (Figure 10b).[89] Similarly, Yang et al. successfully created a wearable temperature sensor using the oxidation-reduction reaction mechanism of [Fe3+/Fe2+]. The device generated variable current signals in response to fluctuations in body temperature, providing key information about the temperature status of the wearer, as shown in Figure 10c. These research findings may have significant relevance in monitoring human activity and predicting potential health risks, making them valuable contributions to the field.[20]In the latest progress, Zhang et al. introduced a thermogalvanic interpenetrating network hydrogel with [Fe(CN)6]3-/[Fe(CN)6]4-as a redox pair and KCl as a ion provider for thermodiffusion, which not only has good flexibility but also prominent thermoelectric property with the thermal current up to 124 μA at the temperature difference of 10 K. Committed to providing more effective medical assistance services.[102]