Flexible iridium oxide based pH sensor integrated with inductively coupled wireless transmission system for wearable applications

Marsh, P., Manjakkal, L. , Yang, X., Huerta, M., Le, T., Thiel, L., Chiao, J.-C., Cao, H. and Dahiya, R. (2020) Flexible iridium oxide based pH sensor integrated with inductively coupled wireless transmission system for wearable applications. IEEE Sensors Journal, 20(10), pp. 5130-5138. (doi: 10.1109/JSEN.2020.2970926)

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Abstract

This work presents a pH sensor platform combining the high performance of iridium oxide (IrOx) fabricated by cyclic voltammetry with inductively-coupled wireless (ICW) transmission. Data included presents flexible potentiometric pH sensors having IrOx as the sensing electrode and a cured Ag/AgCl paste as the pseudo-reference electrode; further investigations concerning performance tailoring via fabrication processes are shown. The fabricated sensors show the best performance with a probe surface area of 1×1 mm2, electrodeposited for 100 cyclic voltammetry (CV) sweeps, at 100 mV/s. The sensitivity of the fabricated sensor is typically in the range of 65–75 mV/pH, as tested using either pH 4–9 (six points) or 2–10 (five points) buffers. The sensors exhibiting those sensitivities in buffer solutions yielded a response from “artificial sweat” solutions differing by ~0.4–0.8 pH from a commercial glass pH electrode, while limit-of-quantification (LOQ) was measured to be ~0.04–0.08 pH. The sensing electrode shows a response time of less than 2 seconds and minimal hysteresis effects. Cationic interferences from up to 1M Na+ resulted in +3–8 mV/pH changes in sensitivity, depending on solution pH and probe, with minimal effects to LOQ. The performance under different bending conditions (0°, 30° at 55 mm radius, 45° at 37 mm, and 90° at 20 mm) of the flexible sensor probe show negligible variation. Finally, the presented sensors were integrated with an inductively coupled wireless (ICW) communication system for a demonstration of online monitoring. This sensor platform can easily be miniaturized due to a low count of necessary components and absence of onboard energy storage.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Dahiya, Professor Ravinder and Manjakkal, Dr Libu
Authors: Marsh, P., Manjakkal, L., Yang, X., Huerta, M., Le, T., Thiel, L., Chiao, J.-C., Cao, H., and Dahiya, R.
College/School:College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
Journal Name:IEEE Sensors Journal
Publisher:IEEE
ISSN:1530-437X
ISSN (Online):1558-1748
Published Online:31 January 2020
Copyright Holders:Copyright © 2020 IEEE
First Published:First published in IEEE Sensors Journal 20(10): 5130-5138
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
170185Engineering Fellowships for Growth: Printed Tactile SKINRavinder DahiyaEngineering and Physical Sciences Research Council (EPSRC)EP/M002527/1ENG - Electronics & Nanoscale Engineering
301728Engineering Fellowships for Growth: Printed Tactile SKINRavinder DahiyaEngineering and Physical Sciences Research Council (EPSRC)EP/R029644/1ENG - Electronics & Nanoscale Engineering