Oxygen Detection Using Different Types of Membranes Deposited on Needle Based Platforms

Abstract

The aim of this work was to develop needle based sensors for oxygen sensing using different types of membranes. For oxygen sensors it is important to achieve fast response time, good linearity, low biofouling and high sensitivity. The effect of different types of polymeric barrier membranes and their various combinations were assessed and compared. An optimized system was thereby selected: sensors covered with polyurethane membrane doped with surfactant showed good stability with a linear working range up to 750 mmHg pO 2. The oxygen sensorGas-permeable materials such as silicone (1), polyethylene, (2) and Nafion (3) have all been introduced into the construction of oxygen sensors. Using this types of materials is important so that to achieve biocompatibility and to control mass transport to the polarised working electrode. To achieve stable O 2 flux is crucial for oxygen sensor reliability, stability and selectivity. Measurement of oxygen is hugely important for clinical medicine. In contrast to blood measurement, however, tissue measurement presents a much more diffusionally limiting matrix. To measure oxygen in tissue, additional, major sensor requirements include minimal invasiveness to minimise tissue damage during implantation. Other important characteristics are good sensitivity, so that low pO 2 values can be registered, minimal oxygen consumption by the cathode to minimise distortion of the measured environment and minimal artefacts introduced by either convection or changes in the oxygen transport properties of the surrounding medium (4). Tissue pO 2 is related to oxygen concentration through the solubility of oxygen in the tissue, i.e. the solubility coefficient of the oxygen in the tissue times the concentration of the dissolved oxygen is equal to the partial pressure of oxygen in that tissue (5). The amperometric detection of oxygen is based on the reduction of dissolved oxygen at a cathode driven by oxygen flux to which in itself is a function of pO 2. Electrode performance variously depends on applied potential, the sensing cathode material, and the resistance of the overall electrochemical circuit. Important is also the surface area of the cathode, temperature, the solubility of oxygen in the electrolyte and the rate of diffusion of oxygen through the covering electrolyte and the membrane barrier layers over the cathode. It is the permeation of oxygen through the membrane that is the function of gas partial pressure. Silicones are highly permeable to oxygen, and as such they are of interest as membrane materials for oxygen sensors. However, as oxygen is also a co-reactant for oxidase based ECS Transactions, 41 (20) 43-48 (2012) 10.1149/1.3687436 © The Electrochemical Society 43 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 10.220.39.222 Downloaded on 2015-07-25 to IP