Flexible Sweat Ph Sensors Based on Tio2-Sno2 Composite Films Prepared by Micro-Arc Oxidation for Wearable Systems

Abstract

This study presents a novel flexible pH sensor based on a dual-electrode configuration, which features a flexible titanium wire micro-arc oxidized electrode as the working electrode and a screen-printed Ag/AgCl reference electrode. The working electrode is coated with a TiO2-SnO2 composite film, which exhibits a highly porous and rugged surface morphology, enhancing the adsorption of electrochemically active species and improving the sensor sensitivity. The screen-printed Ag/AgCl reference electrode demonstrates excellent stability, reversibility, and electrochemical performance, offering a cost-effective alternative to traditional reference electrodes. The sensor exhibits a high sensitivity of 59.74 mV/pH over a wide pH range of 2.00 to 12.00, with a rapid response time of 1 second, low potential hysteresis, and negligible potential drift. Furthermore, the sensor demonstrates good repeatability, stability, and selectivity against common interfering ions, and shows minimal temperature dependence. Its performance remains consistent even after 100 cycles of 45° and 90° bending, highlighting its potential for integration into wearable devices. In a proof-of-concept experiment, the sensor successfully monitored sweat pH on human skin, with results comparable to those obtained using a commercial glass electrode. This study demonstrates the significant potential of the developed flexible pH sensor for wearable technology applications.

Keywords: Flexible pH sensor, Micro-arc oxidation, TiO2-SnO2 composite sensitive films, Ag/AgCl reference electrode