In this paper, we report on an in-house developed electronic nose (E-nose) for use with breath analysis. The unit consists of an array of 10 micro-electro-mechanical systems (MEMS) metal oxide (MOX) gas sensors produced by seven manufacturers. Breath sampling of end-tidal breath is achieved using a heated sample tube, capable of monitoring sampling-related parameters, such as carbon dioxide (CO2), humidity, and temperature. A simple mobile app was developed to receive real-time data from the device, using Wi-Fi communication. The system has been tested using chemical standards and exhaled breath samples from healthy volunteers, before and after taking a peppermint capsule. Results from chemical testing indicate that we can separate chemical standards (acetone, isopropanol and 1-propanol) and different concentrations of isobutylene. The analysis of exhaled breath samples demonstrate that we can distinguish between pre- and post-consumption of peppermint capsules; area under the curve (AUC): 0.81, sensitivity: 0.83 (0.59–0.96), specificity: 0.72 (0.47–0.90), p-value: <0.001. The functionality of the developed device has been demonstrated with the testing of chemical standards and a simplified breath study using peppermint capsules. It is our intention to deploy this system in a UK hospital in an upcoming breath research study.
In this paper, we report on the development of a highly sensitive and humidity-tolerant metal-oxide-based volatile organic compound (VOC) sensor, capable of rapidly detecting low concentrations of VOCs. For this, we successfully fabricated two different thicknesses of nickel oxide (NiO) sensors using a spin-coating technique and tested them with seven different common VOCs at 40% r.h. The measured film thickness of the spin-coated NiO was ~5 μm (S-5) and ~10 μm (S-10). The fastest response and recovery times for all VOCs were less than 80 s and 120 s, respectively. The highest response (Rg/Ra = 1.5 for 5 ppm ethanol) was observed at 350 °C for both sensors. Sensors were also tested in two different humidity conditions (40% and 90% r.h.). The humidity did not significantly influence the observed sensitivity of the films. Furthermore, S-10 NiO showed only a 3% drift in the baseline resistance between the two humidity conditions, making our sensor humidity-tolerant compared to traditional n-type sensors. Thus, we propose thick-film NiO (10 μm) sensing material as an interesting alternative VOC sensor that is fast and humidity-tolerant.
Conductometric gas sensors (CGS) provide a reproducible gas response at a low cost, but their operation mechanisms are not yet well understood. In this paper, we elucidate the nature of...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.