Monolithic MEMS quadrupole mass spectrometers by deep silicon etching

Geear, M.C.; Syms, R.R.A.; Wright, S. L.; Holmes, Andrew S.

doi:10.1109/jmems.2005.851799

Cited by 105 publications

(81 citation statements)

References 32 publications

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“…The data in Figure 4 were obtained with the bias on all lenses and tunnels set to zero, to compare only the geometrical aspects of the various designs. In a previous paper [16], the focusing action of lens 2 with lens 1 and the tunnels held at 0 V was described. This Einzel lens arrangement resulted in a distinct maximum at ϩ8 V when the ion energy was 10 eV.…”

Section: Resultsmentioning

confidence: 99%

“…Silicon-based microelectromechanical systems (MEMS) design approaches are ideally suited to the solution of these problems, as techniques for fabricating complex, multi-layer structures with micrometer precision are well-advanced. Quadrupoles [5,6,[15][16][17] and traps [18,19] have been constructed using MEMS technology, with varying degrees of success.…”

mentioning

confidence: 99%

“…The design is based on the use of bonded silicon on insulator (BSOI), a material consisting of two layers of silicon separated by an insulating layer of silicon oxide, which has become popular for both microelectronic and microengineering applications [26]. We have previously described details of the fabrication process, including mask design and process steps [16,27]. BSOI can be structured using photolithography and deep reactive ion etching (DRIE) [28].…”

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confidence: 99%

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Comparison of ion coupling strategies for a microengineered quadrupole mass filter

Wright¹,

Syms

O'Prey³

et al. 2009

J. Am. Soc. Mass Spectrom.

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The limitations of conventional machining and assembly techniques require that designs for quadrupole mass analyzers with rod diameters less than a millimeter are not merely scale versions of larger instruments. We show how silicon planar processing techniques and microelectromechanical systems (MEMS) design concepts can be used to incorporate complex features into the construction of a miniature quadrupole mass filter chip that could not easily be achieved using other microengineering approaches. Three designs for the entrance and exit to the filter consistent with the chosen materials and techniques have been evaluated. The differences between these seemingly similar structures have a significant effect on the performance. Although one of the designs results in severe attenuation of transmission with increasing mass, the other two can be scanned to m/z ϭ 400 without any corruption of the mass spectrum. At m/z ϭ 219, the variation in the transmission of the three designs was found to be approximately four orders of magnitude. A maximum resolution of M/⌬M ϭ 87 at 10% peak height has been achieved at m/z ϭ 219 with a filter operated at 6 MHz and constructed using rods measuring ( nterest in the miniaturization of mass analyzers has been growing rapidly in recent years, largely driven by the need for compact, lightweight systems for use in environmental, security, and space applications. While there have been numerous attempts to make small analyzers, not all can reasonably be called miniature [1]. However, quadrupole mass filters [2-6] and various types of ion traps [7][8][9] with characteristic dimensions of the order of a few millimeters or less have been demonstrated. The size and weight contribution to a complete mass spectrometer system is not the only benefit of a miniaturized quadrupole mass filter. The rf amplitude required to achieve a particular mass range increases with the square of the rod radius. Hence, the rf supplies for miniature filters can be smaller and require less power than those needed for larger filters. More importantly, smaller pumps may be used, as the short path length of ions in the filter means that a higher pressure can be tolerated. Although this paper is focused on miniaturization of the filter, reports on the development of other miniaturized components that might be incorporated into a system, such as ion sources, gauges, and pumps can be found elsewhere [10 -12].The factors that determine the size of a miniature quadrupole mass filter are the required signal level, the accuracy of the construction technique, and the number of rf cycles needed to achieve the desired resolution. Clearly, as the size of the entrance aperture decreases, there will be an inevitable loss of signal, although some of this can be recovered through the use of an array [2,4]. There is a well-known correlation [13] between the fractional geometrical error and ultimate resolution. Hence, one fundamental limitation is set by the accuracy of the fabrication technique and the minimum acceptable resolution. Si...

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Comparison of ion coupling strategies for a microengineered quadrupole mass filter

Wright¹,

Syms

O'Prey³

et al. 2009

J. Am. Soc. Mass Spectrom.

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“…According to the reported papers on miniaturized mass spectrometers, a wide variety of instruments type including ion traps, quadrupole mass filters (QMF) (Geear et al, 2005), magnetic sector mass spectrometers (Diaz et al, 2001a;Diaz et al, 2001b), and TOF mass spectrometers (Cornish&Cotter, 1997;Cotter et al, 1999;Berkout et al, 2001;Ecelberger et al, 2004) were described. The main specifications are summarized in Table 1.…”

Section: Overview Of Miniaturized Mass Spectrometersmentioning

confidence: 99%

Miniaturized Mass Spectrometer in Analysis of Greenhouse Gases: The Performance and Possibilities

Shimma¹,

Toyoda²

2012

Greenhouse Gases - Emission, Measurement and Management

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“…The first is a simple quadrupole fabricated using bonded silicon-on-insulator material [83,84] To construct a complete filter, two dies are stacked together back-to-back so that the quadrupole geometry is formed. In the bonded silicon device, the features etched into the device layers also form sets of entrance and exit electrodes containing central pupils.…”

Section: Mems Quadrupole Mass Filtersmentioning

confidence: 99%

MEMS-Based Nanospray-Ionization Mass Spectrometer

Wright¹,

Syms

Moseley³

et al. 2010

J. Microelectromech. Syst.

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An electrospray ionisation mass spectrometer (ESI-MS) whose main components are all fabricated using silicon microelectromechanical systems (MEMS) techniques is demonstrated for the first time. The ion source consists of a microengineered alignment bench containing a V-groove mounting for a nanospray capillary, an ion extraction electrode, and a pneumatic nebuliser. The vacuum interface consists of two plates, each carrying a 50 µm diameter capillary, that are selectively etched and bonded together to provide a differentially pumped internal cavity. The quadrupole filter consists of a microfabricated frame that provides mountings for stainless steel rods measuring 650 µm in diameter and 30 mm in length. Two different quadrupoles are compared: a firstgeneration bonded silicon device, and a second-generation silicon-on-glass device with a Brubaker prefilter. Differential pumping of a MEMS component is demonstrated for the first time, atmospheric pressure ionisation and ion transfer into vacuum are characterised, ESI-MS operation is demonstrated and spectra are presented for a variety of compounds. KEYWORDS:Mass spectrometry, Electrospray, Quadrupole filter, MEMS IntroductionOver 25 years have passed since an electrospray ionisation (ESI) source was first coupled to a quadrupole mass spectrometer (MS) by Yamashita and Fenn [1]. Since then, ESI-MS has become a workhorse of analytical chemistry, allowing analytes to be ionised at atmospheric pressure with little fragmentation and passed into a vacuum system for analysis.Conventional ESI sources employ spray tips with an internal diameter (ID) of ≈100 µm[2]. In order to establish a Taylor cone and maintain stable emission of charged droplets, minimum flow rates of 0.5 -5 µL min -1 and voltages of 2.5 -4 kV are used. However, it has been convincingly demonstrated that high sensitivity and stable emission can be achieved at much lower flow rates and voltages using spray tips with IDs of ≈ 5 µm, and silica nanospray capillaries with a range of coatings have become widely available [3][4][5][6][7][8].Unfortunately, while these are inexpensive, operator expertise and costly positioning apparatus are often required for stable and reproducible performance.Electrosprayed ions are passed into a low-pressure chamber via a vacuum interface. The simplest interface is a single orifice or capillary that allows gas and entrained ions to pass directly into the vacuum chamber. Clearly, the orifice must be small enough or the pumps large enough to ensure that the pressure is consistent with mass analysis. However, the susceptibility of very small orifices to clogging and the inconvenience of large pumps led to this approach being abandoned. Modern instruments employ one or more stages of 4 differential pumping. Larger orifices can be tolerated since only a fraction of the flow is transmitted to the vacuum chamber, while the majority of the gas load can be pumped away at higher pressure using more modest pumps.The effective transfer of ions and molecules from atmospheric pressu...

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Monolithic MEMS quadrupole mass spectrometers by deep silicon etching

Cited by 105 publications

References 32 publications

Comparison of ion coupling strategies for a microengineered quadrupole mass filter

Comparison of ion coupling strategies for a microengineered quadrupole mass filter

Miniaturized Mass Spectrometer in Analysis of Greenhouse Gases: The Performance and Possibilities

MEMS-Based Nanospray-Ionization Mass Spectrometer

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