Precise, quantitative measurements of the hydration status of skin can yield important insights into dermatological health and skin structure and function, with additional relevance to essential processes of thermoregulation and other features of basic physiology. Existing tools for determining skin water content exploit surrogate electrical assessments performed with bulky, rigid, and expensive instruments that are difficult to use in a repeatable manner. Recent alternatives exploit thermal measurements using soft wireless devices that adhere gently and noninvasively to the surface of the skin, but with limited operating range (∼1 cm) and high sensitivity to subtle environmental fluctuations. This paper introduces a set of ideas and technologies that overcome these drawbacks to enable high-speed, robust, long-range automated measurements of thermal transport properties via a miniaturized, multisensor module controlled by a long-range (∼10 m) Bluetooth Low Energy system on a chip, with a graphical user interface to standard smartphones. Soft contact to the surface of the skin, with almost zero user burden, yields recordings that can be quantitatively connected to hydration levels of both the epidermis and dermis, using computational modeling techniques, with high levels of repeatability and insensitivity to ambient fluctuations in temperature. Systematic studies of polymers in layered configurations similar to those of human skin, of porcine skin with known levels of hydration, and of human subjects with benchmarks against clinical devices validate the measurement approach and associated sensor hardware. The results support capabilities in characterizing skin barrier function, assessing severity of skin diseases, and evaluating cosmetic and medication efficacy, for use in the clinic or in the home.

精确，定量地测量皮肤的水合作用状况，可以深入了解皮肤病健康状况，皮肤结构和功能，并与基本的体温调节过程和其他基本生理特征相关。用于确定皮肤含水量的现有工具利用难以使用可重复使用的笨重，刚性且昂贵的仪器来替代进行的电气评估。最新的替代方法是利用软无线设备进行热测量，该软设备可以温和且无创地粘附在皮肤表面，但操作范围有限（〜1 cm），并且对细微的环境波动具有很高的灵敏度。本文介绍了一套克服这些缺点的想法和技术，以实现高速，强大，通过微型多传感器模块对热传输特性进行远程自动测量，该模块由芯片上的远程（〜10 m）蓝牙低功耗系统控制，并带有标准智能手机的图形用户界面。与皮肤表面的软接触几乎没有用户负担，所产生的记录可以使用计算建模技术定量地连接到表皮和真皮的水合水平，并且具有高水平的可重复性，并且对环境温度波动不敏感。对类似于人类皮肤，具有已知水合水平的猪皮肤以及具有针对临床设备基准的人类对象进行分层配置的聚合物的系统研究验证了测量方法和相关的传感器硬件。