Iridium Oxide-Based Potassium Sensitive Microprobe With Anti-Fouling Properties

Krzysztof Wildner,Michael Thompson,Brian De La Franier,Khalid Baig Mirza,Simon Cork,Christofer Toumazou,Konstantin Nikolic

doi:10.1109/jsen.2020.3003040

Abstract

Here, we present a new type of potassium sensor which possesses a combination of potassium sensing and anti-biofouling properties. Two major advancements were required to be developed with respect to the current technology; Firstly, design of surface linkers for this type of coating that would allow deposition of the potassium-selective coating on Iridium (Ir) wire or micro-spike surface for chronic monitoring for the first time. As this has never been done before, even for flat Ir surfaces, the material's small dimensions and surface area render this challenging. Secondly, the task of transformation of the coated wire into a sensor. Here we develop and bench-test the electrode sensitivity to potassium and determine its specificity to potassium versus sodium interference. For this purpose we also present a novel characterisation platform which enables dynamic characterization of the sensor including step and sinusoidal response to analyte changes. The developed sensor shows good sensitivity (<; 1 K + ions) and selectivity (up to approximately 10 times more sensitive to K + than Na + concentration changes, depending on concentrations and ionic environment). In addition, the sensor displays very good mechanical properties for the small diameter involved (sub 150μm), which in combination with anti-biofouling properties, renders it an excellent potential tool for the chemical monitoring of neural and other physiological activities using implantable devices.

Highlights

A BNORMAL values of potassium (K+) concentration in tissue have been associated with several conditions such as epilepsy, neuromuscular ataxia, cardiac arrhythmia, Manuscript received March 24, 2020; revised June 11, 2020; accepted June 12, 2020
The X-Ray Photoelectron Spectroscopy (XPS) atomic percentages were calculated from high resolution scans
Iridium from the package without cleaning was predominantly found to have carbon, oxygen, and silicon on the surface with virtually no iridium signal present. This suggests a large amount of surface contamination as well as possible oxidation of the surface

Summary

Introduction

A BNORMAL values of potassium (K+) concentration in tissue have been associated with several conditions such as epilepsy, neuromuscular ataxia, cardiac arrhythmia, Manuscript received March 24, 2020; revised June 11, 2020; accepted June 12, 2020. Date of publication June 17, 2020; date of current version October 2, 2020. The associate editor coordinating the review of this article and approving it for publication was Dr Gymama Slaughter. Krzysztof Wildner was with the Department of Electrical and Electronic Engineering, Imperial College London, London SW7 2AZ, U.K. Krzysztof Wildner was with the Department of Electrical and Electronic Engineering, Imperial College London, London SW7 2AZ, U.K He is with the Institute of Metrology and Biomedical Engineering, Warsaw University of Technology, 02-525 Warsaw, Poland

Objectives

Methods

Results

Conclusion