Wearable sensors and devices for physiological monitoring

• The thermophysical parameters of human tissue are very critical in the research and application of medical thermal science, because the thermal conductivity, thermal diffusivity, blood perfusion rate and metabolic rate are the most basic thermophysical parameters included in all kinds of biological tissue heat transfer models, which are the premise for revealing the heat transfer capacity and heat carrying capacity of biological materials and further bioheat transfer research. Because biological tissues simultaneously have solid heat conduction and blood flow heat transfer, there is also a metabolic heat source inside, and these parameters are not uniformly distributed, they change with space and even temperature, and non-invasive measurement of these parameters, especially their spatial changes are extremely difficult. Therefore, the determination of thermal properties of biological tissues, especially living tissues, is also one of the most significant topics in the field of bioheat transfer. This team studies wearable sensors and devices compatible with human skin to quickly and accurately obtain relevant physical signs data and establish the corresponding relationship between them and the body state, so as to quickly judge or predict the health status of the human body and provide reliable and timely clinical judgment for subsequent medical programs.

  Harmonic-wave flexible wearable sensor: Based on Pennes equation and harmonic detection principle, it can flexibly adjust the depth of thermal wave detection, so as to extract the thermal conductivity, water content and subcutaneous blood perfusion rate of skin epidermis, dermis, subcutaneous fat layer and muscle layer respectively. With a depth of 6 mm, the technology can detect signs of serious skin diseases such as psoriasis, dry skin, and eczema, compared to conventional skin diagnostic instruments that can only detect the stratum corneum (10-20 μm).

  

  Harmonic-wave method rigid wearable sensor: Based on the harmonic method layered detection principle, the thermal conductivity of the epidermis layer (within 1 mm under the skin) and dermis layer (1-3 mm under the skin) can be extracted at the same time, which can indicate the body state more accurately than the traditional method that can only reflect the overall thermal conductivity of the skin. Through a population test (30 people) showed that the epidermal thermal conductivity can reflect the movement of the human body and the change of the ambient temperature, and the dermal thermal conductivity can indicate the female physiological cycle. This technology has potential application value in guiding the daily non-invasive health monitoring of human body.