Preliminary Study on Simultaneous Measurements of Gas and Gap by Using a Planar Coil-Shaped Component Made of MWCNTs at Room Temperature

A planar coil-shaped component based on multiwalled carbon nanotubes (MWCNTs) was fabricated by sputtering and spraying, and the feasibility of the ability of the component to measure gas and gap simultaneously at room temperature in the narrow gap environment of complex equipment was preliminarily verified. The coil-shaped component sprayed with 10 s of MWCNT dispersion has excellent sensitivity, stability, and a signal-to-noise ratio, with a gap ranging from 0 to 5 mm between the coil-shaped element and the copper plate, within the ethanol vapor concentration range of 0–5000 ppm. The gas sensitivity of the impedance amplitude, impedance angle, and resistance reached 0.382%, 0.178%, and 3.935%, respectively, when the ethanol vapor concentration was 5000 ppm. The absolute/relative sensitivities of the impedance amplitude and impedance angle to the gap reach <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3083.36~\Omega \cdot $ </tex-math></inline-formula>mm<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{1}}$ </tex-math></inline-formula>/1.16568%<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula>mm<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{1}}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.92106^{\circ }\cdot $ </tex-math></inline-formula>mm<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{1}}$ </tex-math></inline-formula>/3.59577%<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula>mm<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{1}}$ </tex-math></inline-formula>, respectively, in the gap interval of 0–1 mm. A signal separation method is proposed for simultaneously measuring the gas concentration and gap. The gas concentration can be obtained by resistance, and the gap can be obtained by the impedance variation, which changes only with the gap. These findings lay the foundation for future research on multiparameter measurements of e-skin sensors and gap sensors.