Printed circuit board integrated wearable ion-selective electrode with potential treatment for highly repeatable sweat monitoring

Abstract

Wearable chemical sensors have recently received great attention, especially on monitoring ion concentration in sweat. However, challenges still remain, such as the nonnegligible potential deviation of the ion-selective electrode (ISE) based potentiometric sensor after multi-use. Herein, we propose an easily prepared and highly integrated wearable solid contact-ISE (SC-ISE), allowing multiple measurements with repeatable open circuit potential (OCP), which is achieved by applying a positive potential on the working electrode. It’s believed that the positive potential alters the oxidation-reduction state of the conducting polymer. The integrated SC-ISE sensor is fabricated on a printed circuit board (PCB) substrate, eliminating external hardware. Preparation of the sensor electrode adopts a standard route, i.e. employing the electroless nickel immersion gold (ENIG) process for plating gold layers. Dual working electrodes have been designed to measure either sodium or potassium ion. This wearable platform has been validated through on-body tests by monitoring ion levels in the real sweat.