A Si-Micromachined 162-Stage Two-Part Knudsen Pump for On-Chip Vacuum

Abstract

This paper investigates a two-part architecture for a Knudsen vacuum pump with no moving parts. This type of pump exploits the thermal transpiration that results from the free-molecular flow in nonisothermal channels. For a high compression ratio, 162 stages are serially cascaded. The two-part architecture uses 54 stages designed for the pressure range from 760 to ≈50 Torr, and 108 stages designed for lower pressures. This approach provides greater compression ratio and speed than using a uniform design for each stage. Finite element simulations and analytical design analysis are presented. A five-mask singlewafer fabrication process is used for monolithic integration of the Knudsen pump that has a footprint of 12 × 15 mm 2 . The pressure levels of each stage are measured by integrated Pirani gauges. Experimental evaluation shows that, using an input power of ≈0.39 W, the evacuated chamber is reduced from 760 to ≈0.9 Torr, resulting in a compression ratio of ≈844. The vacuum levels are sustained during 37 days of continuous operation.[2013-0138]

Fabrication of on‐chip vacuum pump using a silicon nanostructure by metal‐assisted chemical etching

“…). The vacuum level achieved was 85.9 kPa, which was much lower vacuum level than that reported in Ref (6.4 kPa). In that study, the heaters were fabricated near the channels, while the heaters in our device heat the entire top side of the device.…”

“…The pump works by the temperature distribution alone, without any mechanical parts, and can be constructed in a small size. Microfabricated Knudsen pumps were reported in previous work . Nanochannels are essential components of these pumps.…”

Molecular tagging velocimetry by direct phosphorescence in gas microflows: Correction of Taylor dispersion

“…The last two decades have witnessed a rapid development of micro-electromechanical systems (MEMS) leading to the emergence of a number of new microfluidic applications involving gas microflows in various technical fields. Gas microflows are notably involved in micro heat exchangers [1] designed for chemical applications or for cooling electronic components, in fluidic micro-actuators developed for active flow control purposes [2], in micronozzles used for the micropropulsion of nano and picosats [3], in micro gas chromatographs [4], gas analyzers [5] or gas separators [6], in vacuum generators and in Knudsen micropumps [7] as well as in some microfluidic-based in vitro devices such as artificial lungs [8]. Similar flows are also observed in porous media with applications relative to the extraction of shale gas [9].…”

Velocity Measurements in Channel Gas Flows in the Slip Regime by means of Molecular Tagging Velocimetry

“…The development of new microfabrication techniques has made the design of novel MEMS possible, highly increasing the range of possible practical applications. There are many examples of MEMS that found a commercial application and that are present in many of our daily life utilities, such as microaccelerometers for smartphones, micronozzles [1] for space applications, microactuators [2] for aeronautical applications, micro heat exchangers [3], and Knudsen pumps [4], to name just a few.…”