A Microvalve Module with High Chemical Inertness and Embedded Flow Heating for Microscale Gas Chromatography

Lu, Hsueh-Tsung; Qin, Yutao; Gianchandani, Yogesh B.

doi:10.3390/s21020632

Cited by 4 publications

(2 citation statements)

References 43 publications

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“…Each microvalve incorporated a prefabricated polyimide valve membrane which was actuated by a latching solenoid actuator (#151082-234, Ledex, CA, USA). Each valve module was housed within a custom housing 3D-printed from Ultem 1010 [ 50 ].…”

Section: Design and Implementationmentioning

confidence: 99%

Progressive Cellular Architecture in Microscale Gas Chromatography for Broad Chemical Analyses

Liao

Zhao

et al. 2021

Sensors

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Gas chromatography is widely used to identify and quantify volatile organic compounds for applications ranging from environmental monitoring to homeland security. We investigate a new architecture for microfabricated gas chromatography systems that can significantly improve the range, speed, and efficiency of such systems. By using a cellular approach, it performs a partial separation of analytes even as the sampling is being performed. The subsequent separation step is then rapidly performed within each cell. The cells, each of which contains a preconcentrator and separation column, are arranged in progression of retentiveness. While accommodating a wide range of analytes, this progressive cellular architecture (PCA) also provides a pathway to improving energy efficiency and lifetime by reducing the need for heating the separation columns. As a proof of concept, a three-cell subsystem (PCA3mv) has been built; it incorporates a number of microfabricated components, including preconcentrators, separation columns, valves, connectors, and a carrier gas filter. The preconcentrator and separation column of each cell are monolithically implemented as a single chip that has a footprint of 1.8 × 5.2 cm2. This subsystem also incorporates two manifold arrays of microfabricated valves, each of which has a footprint of 1.3 × 1.4 cm2. Operated together with a commercial flame ionization detector, the subsystem has been tested against polar and nonpolar analytes (including alkanes, alcohols, aromatics, and phosphonate esters) over a molecular weight range of 32–212 g/mol and a vapor pressure range of 0.005–231 mmHg. The separations require an average column temperature of 63–68 °C within a duration of 12 min, and provide separation resolutions >2 for any two homologues that differ by one methyl group.

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Section: Design and Implementationmentioning

confidence: 99%

Progressive Cellular Architecture in Microscale Gas Chromatography for Broad Chemical Analyses

Liao

Zhao

et al. 2021

Sensors

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“…The analytical performance of a μGC can be affected by the valves located in critical segments of the flow path connecting the sample inlet, the preconcentrator, the separation columns, and the detectors. Some systems incorporate inert and even heated microvalves, , which require specialized fabrication and assembly. Some systems have used Dean’s switches or eliminated valves by merging the sampling and separation flow paths and using a bidirectional pump to provide the sampling and separation flow .…”

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confidence: 99%

Highly Integrated μGC Based on a Multisensing Progressive Cellular Architecture with a Valveless Sample Inlet

et al. 2023

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Microscale gas chromatographs (μGCs) promise infield analysis of volatile organic compounds (VOCs) in environmental and industrial monitoring, healthcare, and homeland security applications. As a step toward addressing challenges with performance and manufacturability, this study reports a highly integrated monolithic chip implementing a multisensing progressive cellular architecture. This architecture incorporates three μGC cells that are customized for different ranges of analyte volatility; each cell includes a preconcentrator and separation column, two complementary capacitive detectors, and a photoionization detector (PID). An on-chip carrier gas filter scrubs ambient air for the analysis. The monolithic chip, with all 16 components, is 40.3 × 55.7 mm 2 in footprint. To accommodate surface adsorptive and low-volatility analytes, the architecture eliminates the commonly used inlet valve, eliminating the need for chemically inactive surfaces in the valves and pumps, allowing the use of standard parts. Representative analysis is demonstrated from a nonpolar 14-analyte mixture, a polar 12-analyte mixture, and a 3-phosphonate ester mixture, covering a wide vapor pressure range (0.005−68.5 kPa) and dielectric constant range (1.8−23.2). The three types of detectors show highly complementary responses. Quantitative analysis is shown in the tens to hundreds ppb range. With 200 mL samples, the projected detection limits reach 0.12− 4.7 ppb. Limited tests performed at 80% humidity showed that the analytes with vapor pressures <12 kPa were unaffected. A typical full run takes 28 min and consumes 2.3 kJ energy for the fluidic elements (excluding electronics). By eliminating chip-to-chip fluidic interconnections and requiring just one custom-fabricated element, this work presents a path toward high-performance and highly manufacturable μGCs.

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Microfluidic flow tuning via asymmetric flow of nematic liquid crystal under temperature gradient

Li,

Yu,

Duan

et al. 2024

Physics of Fluids

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In this work, efficient microfluidic flow rate tuning based on the asymmetric flow of nematic liquid crystal 5CB under a horizontal temperature gradient is studied. Rectangular microchannels with the width of 100 μm are fabricated through soft lithography and treated with homeotropic surface anchoring conditions. Polarized optical microscopy is applied to explore the unique optical anisotropic characteristics of the nematic liquid crystal. The asymmetric velocity profiles in the microchannel are obtained by particle tracking velocimetry. The effects of temperature, flow rate, and aspect ratio on the velocity profile and split ratio of the asymmetric flow are quantitatively studied for the first time, while the mechanism of the flow asymmetry of the nematic liquid crystal is discussed. The results show that the asymmetric flow of the nematic liquid crystal occurs after the horizontal temperature gradient is applied, with the velocity in the heated region markedly higher than its counterpart. The split ratio of the asymmetric flow increases with the increase in the temperature gradient and the decrease in the flow rate. The aspect ratio influences the asymmetric flow through approaches of average velocity and surface anchoring strength, while the former is more distinct. The impacts of temperature gradient, flow rate, and aspect ratio on the flow asymmetry of nematic liquid crystals are caused by the coupling between physical properties, velocity field, and director field. Microchannels based on the asymmetric flow characteristics of nematic liquid crystals can act as a novel kind of temperature-controlled microvalve to achieve efficient microfluidic flow tuning.

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A Microvalve Module with High Chemical Inertness and Embedded Flow Heating for Microscale Gas Chromatography

Cited by 4 publications

References 43 publications

Progressive Cellular Architecture in Microscale Gas Chromatography for Broad Chemical Analyses

Progressive Cellular Architecture in Microscale Gas Chromatography for Broad Chemical Analyses

Highly Integrated μGC Based on a Multisensing Progressive Cellular Architecture with a Valveless Sample Inlet

Microfluidic flow tuning via asymmetric flow of nematic liquid crystal under temperature gradient

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