Sensors

Sensor Research Overview

The Easton lab is interested in novel materials and electrode structures that enhance the sensing performance. In particular, we have been studying electrode structures prepared from materials typically used in power generating fuel cell devices towards the detection of other small molecules such as glucose[1] and ethanol[2, 3]. In addition to demonstrating enhanced sensitivity over existing technologies, we have also developed, validated and enhanced electrochemical diagnostic techniques that enable in situ determination of a sensor fails and whether or not these failures can be recovered.

Breathalyzer Research

A common type of electrochemical sensor is the breath alcohol sensor, more commonly referred to as a breathalyzer. Ethanol is detected electrochemically using a fuel cell-based sensory design, as shown in Figure 1. The electrochemical sensor consists of two platinum based electrodes sandwiched across a polymer electrolyte membrane (PEM) to form what is called the membrane-electrode assembly (MEA).  Ethanol vapor is aspirated into the anode compartment where it is oxidized to several possible products; mainly acetaldehyde, acetic acid and possibly CO2. Protons migrate through the PEM and electrons are transported through the external circuit and into the cathode compartment where they combine with oxygen (from air) to form water. The current (or charge) transferred is measured and is proportional to the concentration/amount of ethanol introduced into anode compartment. Thus, after calibration, the sensor can determine ethanol concentrations in unknown samples, including blood alcohol concentration levels in humans.

Our research efforts in this field is focused on reducing the cost associated with the materials as well as the operating cost of the devices. To do this, we introduce modifications to the structure of the sensor MEA and evaluate performance and stability compared to commercial sensor MEAs. Furthermore, we can subject these samples to accelerated stress tests that mimics the rigors and environmental conditions these sensors experience during field operation. This enables us to rapidly identify the factors that promote loss of sensitivity and understand why certain materials are more (or less) likely to failure during operation.

 

Figure 1: Left: Schematic diagram of a breath alcohol sensor. Middle: The electrochemical response to injection of ethanol vapour from solutions that simulate variable blood alcohol concentrations (BAC) using a sensor prepared using the JM20 catalyst. Right: Comparison of the sensitivity of breath alcohol sensors prepared using different catalysts [3].

More details on our research in this area can be found in the following publications:

[1] M.R. Rahman, J.T.S. Allan, M.Z. Ghavidel, L.E. Prest, F.S. Saleh, E.B. Easton, The application of power-generating fuel cell electrode materials and monitoring methods to breath alcohol sensors, Sensor Actuat B-Chem, 228 (2016) 448-457.

[2] J.T.S. Allan, L.E. Prest, E.B. Easton, The sulfonation of polyvinyl chloride: Synthesis and characterization for proton conducting membrane applications, Journal of Membrane Science, 489 (2015) 175-182.

[3] M.R. Zamanzad Ghavidel, M. R. Rahman, E. B. Easton, "Fuel cell-based breath alcohol sensors utilizing Pt-alloy electrocatalysts", Sensors and Actuators B: Chemical, 273 (2018) 574 – 584.

[4] J.T.S. Allan, M. R. Rahman, E. B. Easton, "The effect of the gas diffusion layer on the performance of fuel cell catalyst layers in ethanol sensors", Sensors and Actuators B: Chemical, 254 (2018) 120 – 132.

[5] J.T.S. Allan, M. R. Rahman, E. B. Easton, "The influence of relative humidity on the performance of Fuel Cell catalyst layers in ethanol sensors", Sensors and Actuators B: Chemical, 239 (2017) 120 – 130.

[6] M. Ammam, E.B. Easton, High-performance glucose sensor based on glucose oxidase encapsulated in new synthesized platinum nanoparticles supported on carbon Vulcan/Nafion composite deposited on glassy carbon, Sensor Actuat B-Chem, 155 (2011) 340-346.