Non‐Invasive Skin Thermo‐Diagnosis Based on a Harmonic Wave‐Driven Wearable Sensor

Abstract Skin thermo‐diagnosis, i.e., monitoring the skin thermal conductivity, can well indicate the body health status. Non‐invasive measurement is the direction of future development for skin thermo‐diagnosis. Here, a rigid and robust wearable sensor driven by the harmonic wave is developed, which can be comfortably wrist‐worn for a long time. Its big advantage is that it can extract both the thermal conductivities of epidermis and dermis (underneath the skin surface by 1 mm or 1–3 mm), which is not implemented by other techniques, and thus can more accurately indicate the possible diseases of the body. A 30‐subject population test shows that the epidermal thermal conductivity exhibits positive dependence on the body surface temperature and the water content, and thus slightly decreased in older subjects whose skin loses its elasticity, water content and nutrients with aging. In a menstrual cycle of women, the dermal thermal conductivity on the date of ovulation is noticeably lower, owing to the significant increase in transdermal water loss and a significant decrease in skin barrier resistance due to the reduction in the cutaneous estrogens. The progress made so far would be an important step toward non‐invasive and convenient monitoring of the human daily health.