Flexible wearable ion humidity sensor developed by Suzhou Nanotechnology for skin moisture detection

Human sweat is rich in a number of potential health and disease-related markers. Compared to conventional blood and urine tests, it has the advantages of non-invasive and real-time continuous monitoring, so the study of wearable sweat sensors It has become one of the focuses of the development of wearable health electronic devices. Miniaturized, integrated all-solid-state ion-selective electrodes and all-solid-state reference electrodes are the core sensing technologies for detecting electrolyte ion concentrations in sweat. However, most of the existing solid-state ion sensors use conductive polymers as ion/electron conductive layer materials, which have the disadvantages of poor stability, many interference factors, and short service life, which limits their application in the field of wearable sweat detection.

Zhang Wei, a research team at the Suzhou Institute of Nanotechnology and Nano-Bionics, Chinese Academy of Sciences, has developed a flexible wearable ion-type humidity sensor (Advanced Science, 2017, 1600404, 1-7, Back Cover) for skin moisture detection. Furthermore, for the key scientific and technical problems such as the miniaturization of all-solid-state ion sensors and the stability of all-solid-state reference electrodes, the research team combined with MEMS micro-nano processing technology to design and prepare electrode chips with microporous arrays as templates, which were prepared by one-step electrodeposition method. The large specific surface area and regulatable three-dimensional gold nanostructure ion/electron conduction array electrode has advantages of simple preparation and good repeatability compared with ion/electron conduction layers based on carbon nanotubes, graphene and porous carbon. . The all-solid ion selective electrode constructed by the electrode chip has stable potential response sensitivity (56.58 ± 1.02mV/decade), fast response time (<10s) and wide linear range (10-6~10-1mol/L) The potential drift of the sensor and the influence of water layer interference are reduced.

By optimizing the composition of the reference electrode polymer film and salt, a polymer/potassium chloride-based all-solid reference electrode is integrated on the sensor chip, and the obtained miniaturized reference electrode chip has a short balance time for different types. It has small interference with different ionic strength electrolytes, is insensitive to light, has stable response in the range of pH 3~10, and has long-term stability and other advantages. At the same time, the research team innovatively designed a wearable “sweatband” sweat sensing device with sweat collection, transport and discharge structure, which integrates the sensor chip and sweat sweat guide tape to comfortably and conveniently wear the human forehead area. It can analyze and monitor the electrolyte ions in real time during the movement of the human body, and monitor the dehydration of people during fitness exercise, especially for the physical health status of athletes, emergency rescue personnel and military personnel in the process of performing high-intensity tasks. And guiding significance. Related research results are published in Analytical Chemistry.

The work was funded by the National Natural Science Foundation of China, the Jiangsu Outstanding Youth Fund, and the China Postdoctoral Science Foundation.

Figure 1 (A) Electrodeposition of three-dimensional gold nanostructured solid-contact conduction array electrodes with different specific surface areas; (B) Schematic diagram of the construction of all-solid-state ion-selective array electrodes

Figure 2 (A), (B) and (C) are photographs and schematic diagrams of wearable "sweatband" sweat sensor devices; (D) calibration curves of sweat sensor chips for different concentrations of standard Na+ solution before and after wearing (E) A graph showing the continuous monitoring of Na+ concentration in sweat in real time during the movement of the sweat sensor on the human body