Moisture-Sensitive and Super Washable Fabric Patches Obtained by Etching Ag-Plated Cloth for Wearable Sweat Sensing

In this article, the washable and flexible fabric interdigital electrode patch is proposed to detect sweat secretion. Leveraging its washability, the electrode is applied for directly absorbing sweat on skin and detecting sweat volume in it by measuring the variation in capacitance value of the interdigital electrode. To make the fabric electrode washable and reusable, we etch washable Ag-coated conductive cloth to form the fabric interdigital electrode with the remaining Ag coating. The patch retains the durability and washable resistance of the Ag-coated conductive cloth. The fabric interdigital electrode patch is a completely woven structure and completely permeable to water or air. Sweat can freely penetrate in the Ag-plated fabric inside the patch, making the interdigital electrode highly sensitive to sweat. In the test, 0.01 mL of sweat can increase the capacitance in the electrode by an order of magnitude. By fitting the relationship between sweat volume in the electrode and capacitance, one can detect the amount of sweat secretion based on the capacitance. Furthermore, the relationship between capacitance and sweat volume remains stable through multiple absorptions of sweat and repeated cleaning. The relationship also remains stable across different fabric electrode patches.