Electronic nose (E-nose) technology provides an easy and inexpensive way to analyse chemical samples. In recent years, there has been increasing demand for E-noses in applications such as food safety, environmental monitoring and medical diagnostics. Currently, the majority of E-noses utilise an array of metal oxide (MOX) or conducting polymer (CP) gas sensors. However, these sensing technologies can suffer from sensor drift, poor repeatability and temperature and humidity effects. Optical gas sensors have the potential to overcome these issues. This paper reports on the development of an optical non-dispersive infrared (NDIR) E-nose, which consists of an array of four tuneable detectors, able to scan a range of wavelengths (3.1–10.5 μm). The functionality of the device was demonstrated in a series of experiments, involving gas rig tests for individual chemicals (CO2 and CH4), at different concentrations, and discriminating between chemical standards and complex mixtures. The optical gas sensor responses were shown to be linear to polynomial for different concentrations of CO2 and CH4. Good discrimination was achieved between sample groups. Optical E-nose technology therefore demonstrates significant potential as a portable and low-cost solution for a number of E-nose applications.

We report on the design, fabrication and verification of a portable, low cost PID. Unlike commercial PID sensors, ours provides two outputs. One output correlates to the total chemical components and a second that provides some level of compositional information. We believe that this makes this sensor system more useful than a standard commercial PID, at a similar cost point. Our PID sensor was tested with gas concentrations down to 2 ppm isobutylene. The results presented indicate that the limit of detection will be well below 1 ppm. Compositional analysis was also carried out and the results presented shows our sensor can successfully discriminate between low concentrations of 2-hexanone, isobutylene, propanol, 2-pentanone, 2-octanone and 2-heptanone.

A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP url' above for details on accessing the published version and note that access may require a subscription.For more information, please contact the WRAP Team at: wrap@warwick.ac.uk Sensors-21054-2018 1  Abstract-In this paper we report on the development of a simple, yet innovative multi-channel olfactory display. Unlike other sensory stimuli (specifically sight and sound), digital olfactory technology has yet to have wide-spread commercial success. Our proposed system will release up to 8 different liquid phase aromas (essential oils) using a thermal mechanism. The unit contains a speed controlled fan, temperature control of the heating element and a gas sensor to provide feedback to inform the release rate. It can be connected (via Bluetooth LE) to a tablet/computer to control the timing and intensity of the aroma. External measurements show that aromas can be detected within a few seconds of release and produce a broad range of intensities from low ppm to 10's of ppm.Index Terms-Aroma generator, digital olfaction, olfactory display. I. INTRODUCTIONHE field of olfaction has remained one of the most underdeveloped technological areas in our modern digital world. Though there have been significant advances in the way that information is presented to us as digital users -be it through visual or audio means, olfaction still appears to be a technology of the future. The reasons for this are complex and potentially associated with a mixture of factors, including the dominance of our other senses, poor training of the population in olfaction and a feeling that it is not an important sense. However, olfaction has the ability to enrich visuals and provide easier access to parts of our brain associated with, for example, long term memory [1].The potential applications for olfactory technology are significant and range from medical applications to virtual reality (VR). This could include helping with anxiety/stress or in the diagnosis of degenerative disorders such as Parkinson's disease. In tourism/museum environments, smells can be used to compliment sound and vision effects of historical sites to relive the past. Other applications include VR and multimedia to enhance gaming, television entertainment and beyond. There have even been attempts to create communication protocols based on gas phase chemical transmission instead of electrical [2]. Considering these applications, it is surprising that olfactory displays are not common throughout society and found in every home. There are a number of potential reasons for this, but one major gap is the lack of a simple, robust digital olfactory technology. These technologies should not be confused with most existing aroma approaches, such as air fresheners, perfumes (with paper smelling strips) or even candles, but are distinct in being able to provide a ra...