On-chip vacuum generated by a micromachined Knudsen pump

McNamara, Shamus; Gianchandani, Yogesh B.

doi:10.1109/jmems.2005.850718

Cited by 107 publications

(79 citation statements)

References 18 publications

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“…At this point an approximation of the efficiency can be obtained using equation (17). A more accurate value for the efficiency can be computed if either the hot T or the cold T is measured or calculated.…”

Section: Methods To Calculate Pump Efficiencymentioning

confidence: 99%

“…Until 1990, the prototypes of the pump had to accomplish this by either increasing the mean free path to the size of the characteristic dimension or by creating pinholes in a membrane [9]. MEMS fabrication has allowed the miniaturization of the Knudsen pump [17]. The Knudsen pump has the advantage over macro scale pumps, that it does not suffer from reduced life cycles due to various modes of mechanical failure.…”

Section: Knudsen Pumpmentioning

confidence: 99%

“…An alternative fabrication method involves using MEMS technologies to fabricate a rectangular channel [17] …”

Section: Knudsen Pumpmentioning

confidence: 99%

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A MEMS Knudsen pump for high gas flow applications.

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Section: Methods To Calculate Pump Efficiencymentioning

confidence: 99%

Section: Knudsen Pumpmentioning

confidence: 99%

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A MEMS Knudsen pump for high gas flow applications.

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“…More than fty years later micro-scale structures, Micro Electro-Mechanical Systems (MEMS) and heat exchangers are common place with applications in medicine, avionics, consumer electronics, process monitoring and automotive engineering to name just a few. Actual devices that require knowledge of the heat and mass transfer characteristics include ow control [2], ow sensing [3], chemical sensors [4,5], micro-pumps [6,7], power generation [8], and heat sinks [9][10][11]. To allow these devices to perform in an optimal manner the designer must have tools that allow design choices to be made with con dence.…”

Section: Sc Schmidt Numbermentioning

confidence: 99%

“…This con guration is the classic Knudsen pump. This method of pumping has the bene t of having no moving parts nor any uids present that may contaminate the ow and has been physically realized in numerous applications [7,27,28].…”

Section: 1mentioning

confidence: 99%

Numerical investigation of gaseous heat and mass transfer: the effect of rarefaction

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Recent advances in micro-scale fabrication have uncovered the limitations of classical uid dynamics analysis techniques. The current status of numerical techniques for micro-ows is found to be highly varied with no accepted best-practice. This situation encourages investigation of new and improved methods in the eld. In this work a new numerical method based upon the solution of the model Boltzmann equation using arbitrary order polynomials is presented. The S-model is solved by a discrete ordinate method with velocity space discretized with a truncated Hermite polynomial expansion. Physical space is discretized according to the Conservative Flux Approximation scheme with extension to allow non-uniform grid spacing. This approach, which utilizes Legendre polynomials, allows the spatial representation and ux calculation to be of arbitrary order. High order boundary conditions are implemented. Various results are shown to demonstrate the utility and limitations of the method with comparison to solutions of the Euler and Navier-Stokes equations and from the Direct Simulation Monte Carlo and Uni ed Gas Kinetic schemes. The e ect of both the velocity space discretization and Knudsen number on the convergence properties of the scheme are also investigated.Due to limitations in the geometric adaptability of the new method an implementation of the Uni ed Gas Kinetic Scheme with a variety of enhancements is also presented. These enhancements include internal degree of freedom handling and advanced gas-surface interaction mechanisms including a model of the adsorption and desorption of gas molecules by a surface.The numerical methods developed are used to investigate physical ow phenomena including rare ed e ects such as thermal creep. Pressure gradient inducing thermal creep driven ows in microchannels, commonly referred to as Knudsen pumps, are investigated across a range of rarefaction with particular focus on the e ects of realistic gas coe cients and geometric con guration on performance.A range of geometries are investigated consisting of a previously proposed curved-straight channel and three newly developed channels including a novel two dimensional matrix pump arrangement and classical linear designs. Use of the S-model kinetic equations enables investigation with realistic values of the Prandtl number and viscosity index for argon and nitrogen as well as for Maxwell molecules. The pumping performance and ow structure of each geometry is investigated for a range of channel aspect ratios and Knudsen numbers where the Knudsen numbers are nely spaced between 0.1 and 2.0 to allow approximate performance extrema to be identi ed. The in uence of Prandtl number is found to be signi cant with increased maximum mass ow rates for argon and nitrogen of 5.5-6% when compared to a gas with Maxwellian molecular model. The impact of speci c heat ratio is found to be comparatively minor with a di erence of 0.5% between the argon and nitrogen. The two new channel designs are found to lie between the classical and existing ...

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Biomimetic Light‐Driven Aerogel Passive Pump for Volatile Organic Pollutant Removal

et al. 2022

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Inspired by the solar-light-driven oxygen transportation in aquatic plants, a biomimetic sustainable light-driven aerogel pump with a surface layer containing black manganese oxide (MnO 2 ) as an optical absorber is developed. The flow intensity of the pumped air is controlled by the pore structure of nanofilbrillated cellulose, urea-modified chitosan, or polymethylsilsesquioxane (PMSQ) aerogels. The MnO 2 -induced photothermal conversion drives both the passive gas flow and the catalytic degradation of volatile organic pollutants. All investigated aerogels demonstrate superior pumping compared to benchmarked Knudsen pump systems, but the inorganic PMSQ aerogels provide the highest flexibility in terms of the input power and photothermal degradation activity. Aerogel light-driven multifunctional gas pumps offer a broad future application potential for gas-sensing devices, air-quality mapping, and air quality control systems.

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On-chip vacuum generated by a micromachined Knudsen pump

Cited by 107 publications

References 18 publications

A MEMS Knudsen pump for high gas flow applications.

A MEMS Knudsen pump for high gas flow applications.

Numerical investigation of gaseous heat and mass transfer: the effect of rarefaction

Biomimetic Light‐Driven Aerogel Passive Pump for Volatile Organic Pollutant Removal

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