Colorimetric Signal Readout for the Detection of Volatile Organic Compounds Using a Printable Glass-Based Dielectric Barrier Discharge-Type Helium Plasma Detector

Abstract

In this paper, we report on a printable glass-based manufacturing method and a new proof-of-concept colorimetric signal readout scheme for a dielectric barrier discharge (DBD)-type helium plasma photoionization detector. The sensor consists of a millimeter-sized glass chamber manufactured using a printable glass suspension. Plasma inside the chip is generated using a custom-built power supply (900 V and 83.6 kHz), and the detector uses ∼5 W of power. Our new detection scheme is based on detecting the change in the color of plasma after the introduction of target gases. The change in color is first captured by a smartphone camera as a video output. The recorded video is then processed and converted to an image light intensity vs retention time plot (gas chromatogram) using three standard color space models (red, green, blue (RGB), hue, saturation, lightness (HSL), and hue, saturation, value (HSV)) with RGB performing the best among the three models. We successfully detected three different categories of volatile organic compounds using our new detection scheme and a 30-m-long gas chromatography column: (1) straight-chain alkanes (n-pentane, n-hexane, n-heptane, n-octane, and n-nonane), (2) aromatics (benzene, toluene, and ethylbenzene), and (3) polar compounds (acetone, ethanol, and dichloromethane). The best limit of detection of 10 ng was achieved for benzene at room temperature. Additionally, the device showed excellent performance for different types of sample mixtures consisting of three and five compounds. Our new detector readout method combined with our ability to print complex glass structures provides a new research avenue to analyze complex gas mixtures and their components.

Identification of Different Classes of VOCs Based on Optical Emission Spectra Using a Dielectric Barrier Helium Plasma Coupled with a Mini Spectrometer

“…The μHDBD-PID used in this work was fabricated and assembled following the same process reported in our earlier work and powered by the same power supply (Figures S1–S2). One key difference in our current study involves direct sample injection into the device using a fused silica capillary tube connected to an Agilent 7820A GC system. Figure a shows the helium plasma generated inside the chamber.…”

“…Our group previously reported a colorimetric signal readout based on micro helium dielectric barrier discharge PID (μHDBD-PID). Our detector was based on detecting changes in image light intensity during injection of different VOCs . This work also required coupling of the detector with a GC column for the reliable identification of different compounds.…”

“…In this work, we present a micro helium DBD-OES (μHDBD-OES) system for detection and identification of VOCs. To reduce the size of our μHDBD-OES system, we previously miniaturized the excitation source . The fabrication of the helium plasma chamber is based on using a combination of 3D printing, molding, and sintering processes.…”

Manufacturing fused silica hemispherical resonators using polymer glass suspension and replication molding

“…The final sintered part possesses chemical and mechanical properties that match those of commercially available FS glass [32]. Complex structures with micro to millimeter dimensions, including those with closed cavities, microfluidic channels [33], three-dimensional structures like resonators [31], and chemical sensors [34,35] can be readily fabricated with this Glassomer material. Our work presents a novel manufacturing technique by using a printable polymer glass mixture for producing HSRs with an approximate rim diameter of 9.6 mm.…”