Heterogeneous metal-oxide nanowire micro-sensor array for gas sensing

Abstract

Vanadium oxide, manganese oxide, tungsten oxide, and nickel oxide nanowires were investigated for their applicability as chemiresistive gas sensors. Nanowires have excellent surface-to-volume ratios which yield higher sensitivities than bulk materials. Sensing elements consisting of these materials were assembled in an array to create an electronic nose platform. Dielectrophoresis was used to position the nanomaterials onto a microfabricated array of electrodes, which was subsequently mounted onto a leadless chip carrier and printed circuit board for rapid testing. Samples were tested in an enclosed chamber with vapors of acetone, isopropanol, methanol, and aqueous ammonia. The change in resistance of each assembly was measured. Responses varied between nanowire compositions, each demonstrating unique and repeatable responses to different gases; this enabled direct detection of the gases from the ensemble response. Sensitivities were calculated based on the fractional resistance change in a saturated environment and ranged from 6 × 10 −4 to 2 × 10 −5 %change ppm −1 .

Chemiresistive Electronic Nose toward Detection of Biomarkers in Exhaled Breath

“…Also, Shin et al synthesized Pt-functionalized SnO 2 fibers via electrospinning and applied them to diagnose diabetes and lung cancer . However, these nanostructures formed by chemical reactions have unstable contacts at high temperatures between themselves, and thus, research focusing on how to integrate them with low cost and high reproducibility in a designed configuration is still in an early stage . As an alternative approach, formation of metal oxide nanostructures by physical vapor deposition (PVD) has been considered more desirable for the CEN in terms of simplicity in synthesis, stability, reproducibility, and excellent compatibility with semiconductor fabrication processes. , …”

Electrically Transduced Gas Sensors Based on Semiconducting Metal Oxide Nanowires

“…Recently, several methods have been developed to improve selectivity, such as pulsed temperature modulation, microdiffusion, use of thermal gradients or cycled-temperature regime [159][160][161][162][163]. Selectivity toward specific gases can also be achieved by optimizing the sensor architecture, designing sensor arrays and training machine-learning-based classifiers (see details in Section 5.1) [30,37,145,157,[164][165][166][167][168][169][170][171][172][173][174].…”