A Monolithic High-Flow Knudsen Pump Using Vertical Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Channels in SOI

An, Sung Yong; Qin, Yutao; Gianchandani, Yogesh B.

doi:10.1109/jmems.2015.2426699

Cited by 24 publications

(30 citation statements)

References 28 publications

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“…The measured performance of silicon micromachined KPs [15,18,19] can be within 15% of the estimate provided by Sharipov's equation. Pressure-driven viscous flow is usually more significant in the KPs that use nanoporous materials because of the nature of these media (which have more tortuosity, non-uniformity, and random defects).…”

Section: Introductionsupporting

confidence: 61%

“…This flow is evident only when viscous flow is suppressed, i.e., under conditions where the collisions between gas molecules do not greatly dominate collisions between gas molecules and the walls of the flow channel. Operation at atmospheric pressure is possible even with hydraulic diameters of ≈2 µm [15]. The pumping direction can be reversed by powering different heaters located at opposing ends of the flow channel.…”

Section: Introductionmentioning

confidence: 99%

“…The parameter that is under the control of the device designer is ∆T. In typical unidirectional implementations of KP that are intended to operate at atmospheric pressure, arrays of nanoscale channels can be provided by either micromachining silicon [15,[17][18][19] or by nanoporous media such as ceramics, zeolites, and polymer membranes [20][21][22][23]. The nanoscale channels are sandwiched between a passive heat sink and a Joule heater to establish the temperature gradient that generates thermal transpiration flow.…”

Section: Introductionmentioning

confidence: 99%

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A Bidirectional Knudsen Pump with a 3D-Printed Thermal Management Platform

2021

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This paper reports on a bidirectional Knudsen pump (KP) with a 3D-printed thermal management platform; the pump is intended principally for microscale gas chromatography applications. Knudsen pumps utilize thermal transpiration, where non-viscous flow is created against a temperature gradient; no moving parts are necessary. Here, a specialized design leverages 3D direct metal laser sintering and provides thermal management that minimizes loss from a joule heater located on the outlet side of KP, while maintaining convective cooling on the inlet side. The 3D-KP design is integrative and compact, and is specifically intended to simplify assembly. The 3D-KP pumping area is ≈1.1 cm2; with the integrated heat sink, the structure has a footprint of 64.2 × 64.2 mm2. Using mixed cellulose ester (MCE) membranes with a 25 nm average pore diameter and 525 μm total membrane thickness as the pumping media, the 3D-KP achieves a maximum flow rate of 0.39 sccm and blocking pressure of 818.2 Pa at 2 W input power. The operating temperature is 72.2 °C at ambient room temperature. In addition to MCE membranes, anodic aluminum oxide (AAO) membranes are evaluated as the pumping media; these AAO membranes can accommodate higher operating temperatures than MCE membranes. The 3D-KP with AAO membranes with 0.2 μm average pore diameter and 531 μm total membrane thickness achieves a maximum flow rate of 0.75 sccm and blocking pressure of 496.1 Pa at 9.8 W at an operating temperature of 191.2 °C.

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Section: Introductionsupporting

confidence: 61%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Bidirectional Knudsen Pump with a 3D-Printed Thermal Management Platform

2021

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“…A variety of µGC components have been reported, typically as standalone elements: preconcentrators [35], valves [36,37], separation columns [38][39][40], detectors [41][42][43][44][45][46], and pumps [47][48][49]. In the PCA3mv, Cell 2 and Cell 3 each used a monolithic chip that integrated a preconcentrator, a separation column, and a T-connector (Figure 3a); Cell 1 did not use a monolithic chip as the coating method for the Column1 stationary phase has not been developed.…”

Section: Microfabricated Componentsmentioning

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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“…The main types of vacuum micropumps include micro diaphragm pumps [22,23], micro vapour-jet pumps [24,25], micro cryopumps [26], Knudsen pumps [27,28,29] and micro ion pumps [30,31,32,33,34]. Micro diaphragm pumps, micro vapour-jet pumps and micro cryopumps can start working at atmospheric pressure and pump gas continuously.…”

Section: Introductionmentioning

confidence: 99%

Cathode Design Optimization toward the Wide-Pressure-Range Miniature Discharge Ion Source for a Vacuum Micropump

Yao

Tang

Zhang

et al. 2019

Sensors

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It is difficult to generate and maintain the vacuum level in vacuum MEMS (Micro-Electro-Mechanical Systems) devices. Currently, there is still no single method or device capable of generating and maintaining the desired vacuum level in a vacuum device for a long time. This paper proposed a new wide-pressure-range miniature ion source, which can be applied to a vacuum micropump. The miniature ion source consists only of silicon electrodes and a glass substrate. Its operating pressure range covers seven orders of magnitude, starting from atmospheric pressure, a promising solution to the difficulty. Based on the principle of gas discharge, the ion source features a simple two-electrode structure with a two-stage electrode spacing, operating under DC voltage excitation. The first-stage electrode spacing of the ion source is small enough to ensure that it starts working at atmospheric pressure down to a certain reduced pressure when it automatically switches to discharge at the larger second-stage electrode spacing and operates from that pressure down to a high vacuum. Two configurations of the ion source have been tested: without-magnet, operating from atmospheric pressure down to 1 mbar; and with-magnet, operating from atmospheric pressure to 10−4 mbar, which covers seven orders of magnitude of pressure. The ion source can be applied not only to a MEMS ion pump to meet demands of a variety of vacuum MEMS devices, but can also be applied to other devices, such as vacuum microgauges and mass spectrometers.

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A Monolithic High-Flow Knudsen Pump Using Vertical Al<sub>2</sub>O<sub>3</sub> Channels in SOI

Cited by 24 publications

References 28 publications

A Bidirectional Knudsen Pump with a 3D-Printed Thermal Management Platform

A Bidirectional Knudsen Pump with a 3D-Printed Thermal Management Platform

Progressive Cellular Architecture in Microscale Gas Chromatography for Broad Chemical Analyses

Cathode Design Optimization toward the Wide-Pressure-Range Miniature Discharge Ion Source for a Vacuum Micropump

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