Configuration of an electrostatic ion trap

Abstract

An electrostatic ion trap or an array of electrostatic ion traps having a longitudinal length of no more than 10 mm and / or at least one electrode with a capacitance to ground of no more than 1 pF is provided. First and second sets of planar electrodes may be distributed along the longitudinal axis, at least some of which are configured to receive an electrostatic potential to confine ions received in the space between the first and second sets of planar electrodes. An array may include an inlet for receiving an ion beam configured such that a portion of the ion beam can be trapped in each of the ion traps. Signals indicative of ion mass and charge data may be obtained from multiple electrostatic ion traps in the array.These mass and charge data can be combined to identify components of a mixture of different analyte ions.

Description

TECHNICAL FIELD OF REVELATION

[0001] The disclosure relates to electrostatic ion traps, arrays of electrostatic ion traps, and methods for analyzing an ion beam. CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. patent application 17 / 823,618, filed August 31, 2022, which is incorporated herein by reference. BACKGROUND OF REVELATION

[0003] High-resolution analyzers for accurate mass determinations (HR / AM analyzers) that utilize electrostatic fields are well known. These include: multiple reflection time-of-flight (mrTOF) analyzers with destructive ion detection (e.g., using secondary electron multipliers), including those described in WO2013110587, WO2019202338, WO2017087470 and references therein; orbital trap mass analyzers, including those described in US5886346, US7767960, US7985950; and electrostatic ion traps with closed and open trajectories, including those described in US5880466, US9728384, US10453668, and DZ Keifer et al., Analyst 142, 1654 (2017).

[0004] Orbital trap mass analyzers and some other electrostatic ion traps use an image current for non-destructive ion detection. With sufficiently low capacitance of the detection electrodes and transistors of a preamplifier, it is possible to detect individual ions even over extended detection times. This is practiced, for example, in charge detection mass spectrometry (CDMS), as described in US11232941, US11227759, and US2022068624. Recently, the detection of a single elementary charge was demonstrated by AR Todd et al., J. Am. Soc. Mass Spectrom. 2020, 31, 146-154.

[0005] The productivity of existing HR / AM analyzers is limited to a few dozen to a few hundred spectra per second. Therefore, for efficiency reasons, as many species as possible are crammed into a single MS or MS / MS spectrum until the space charge limit is reached. Space charge effects can ultimately limit the dynamic range and depth of analysis.

[0006] As a result, such analyzers can identify no more than 10 to 100 of the most abundant species per second. Although this rate has increased dramatically in recent years due to the widespread adoption of fast liquid chromatography and data-independent data acquisition (DIA), new approaches are needed for the next leap in productivity, particularly in proteomics.

[0007] Recent breakthroughs in the informatics foundations of DIA, including the introduction of machine learning, have dramatically improved the reliability of deconvolution of mixed spectra into single fragment spectra. This approach may work reliably for the most intense components of mixed spectra, but it is not applicable to species at the lower end of the dynamic range, as these are represented by only a few ions. This ultimately limits the depth of analysis, particularly in proteomics, where the dynamic range of concentrations can exceed 10 to 12 orders of magnitude. The problem is even more acute in single-cell proteomics, where the total number of peptides available for analysis is limited to a few billion per cell, and only a few hundred million ions actually make it into a mass spectrometer.

[0008] Various enrichment techniques have been tried, either on the sample preparation side (Seer, fractionation) or on the ion sorting side (as shown, for example, in US9812310, US10199208). These techniques typically involve generating a number of fractions that must then be analyzed either individually or in batches. While these approaches appear to provide better performance, they do not perform equally well for all species, resulting in a number of low-abundance species being unrepresented or even lost in the process. At the same time, analyzing fractions individually in the same mass analyzer proportionally reduces throughput, as a mass analyzer is essentially a single-channel device.

[0009] To address this throughput problem, arrays of mass analyzers have been considered. Electrostatic ion trap arrays have been extensively studied, including, for example, in US5206506, US7718959, US2003089846, US6762406, WO2006049623, US9779930, WO2021061650, and US7985950 (in the form of orbital trap mass analyzers). Arrays of some other analyzers have also been considered, for example, in US7985950, US10049867, US10593533, and US2008067349. All of these transport ions across three dimensions to make the entire multi-analyzer mass spectrometer space-efficient. However, high-resolution capabilities for accurate mass determinations in such arrays have proven difficult due to inherent limitations in electrode accuracy.

[0010] To address these challenges, improvements in electrostatic ion traps and mass analyzer arrays are desirable. SUMMARY OF REVELATION

[0011] Against this background, an electrostatic ion trap according to claim 1, an arrangement of electrostatic ion traps according to claim 26, and a method for analyzing an ion beam comprising a mixture of different analyte ions according to claim 32 are provided. Preferred and / or optional features are disclosed in the dependent claims.

[0012] A new type of microscale electrostatic ion trap (µEST) is proposed, wherein the typical length of the trap is no more than 10 mm and optionally no more than 5 mm, 2 mm, 1 mm, or 0.5 mm. Additionally or alternatively, the capacitance of at least one of the electrodes (in particular a detection electrode) to ground is no more than 1 pF. The µEST advantageously comprises planar electrodes distributed along a longitudinal axis (z-dimension). Each electrode extends perpendicular to the longitudinal axis (in a width or x-dimension). One set of electrodes distributed along the longitudinal axis is spaced from a second set of electrodes (also parallel to the longitudinal axis) to define a trapping region between the sets of electrodes (and defining a height or y-dimension). To confine the ions received in the trapping region, electrostatic potentials are applied to at least some of the electrodes.For an improved field, the two sets of electrodes can mirror each other in their configuration. Implementing the trap electrodes in the submillimeter range, preferably with nanometer tolerance, enables high resolution. The µEST can have a controller to configure its operation, or a group of µESTs can share a controller. A controller can include a processor and a computer program configured to run on the processor.

[0013] Due to its small size and the use of electrostatic potentials to trap ions, the µEST allows the confinement of a small number of ions, generally no more than 100, 50, 30, 20, 10, 5 charged particles, or even a single charged particle, in a small space. Nevertheless, high-resolution analysis for accurate mass determinations is possible. This opens up new types of ion analysis. A measurement time of no more than 20 ms and / or an accelerating voltage of no more than 200 V and / or a gas pressure within the electrostatic ion trap of no more than 10 -7mbar is achievable. Furthermore, the µEST can be manufactured efficiently and cost-effectively, for example, using lithographic techniques. The µEST could be formed as part of an integrated circuit. Modern micro- and nanolithography technologies could make it possible to achieve nanometer-scale tolerances on planar wafers.

[0014] One or more of the electrodes (usually toward the center of the trap along the longitudinal axis) is used for ion detection by an induced image current. Reliable image current detection of individual elementary charges is enabled by the microscale design of the trap. As stated above, the capacitance of one, some, or each detection electrode(s) to ground is kept low, typically to no more (or less) than 1 pF, 500 fF, 100 fF, 50 fF, 10 fF, 5 fF, or 1 fF. Such a low capacitance can enable the detection of a single charge. A transistor (e.g., a FET or JFET) can be connected to the detection electrode(s), which can also be lithographically formed.

[0015] Some of the electrodes (usually the outer electrodes) can be used to reflect the ions by applying a suitable potential. Other electrodes, generally between the reflecting electrodes and the detecting electrodes, can receive a suitable potential to accelerate the ions. By reducing the potentials at the reflecting electrodes, ions can be allowed to enter the trap. The potentials at the reflecting electrodes can then be increased to confine the ions to the trapping region. A distance between adjacent electrodes in the longitudinal (or Z) dimension is generally no more than 100 µm, preferably no more than 50 µm, and usually much smaller, for example, no more (or less) than 20 µm, 10 µm, or 5 µm.A distance (e.g. free space) between electrodes at different levels (in the height or y-dimension) is generally not more or less than 100 µm and usually not more or less than 80 µm or 70 µm.

[0016] Each electrode set may be formed on a respective planar substrate (e.g., a wafer). To form the µEST, the two substrates may be positioned so that the electrodes face each other. A spacer (or multiple spacers) may separate the electrode sets (or substrates or wafers). The spacer(s) may include conductive spacers for electrically coupling the electrodes.

[0017] In some embodiments, the arrangement of each set of electrodes is substantially symmetrical between opposite sides of a center of the electrostatic trap along the longitudinal axis (line z=0). Additionally or alternatively, one or both edges of at least some of the electrodes along the longitudinal axis have an arcuate shape. For example, some of the electrodes may have a curved shape, an arcuate shape, a circular shape, or an elliptical shape. The curved shape enables improved ion containment when using planar electrodes.

[0018] A corrugated, modulated, or multiply curved shape of the boundary between adjacent electrodes can be further advantageous. Since the electrostatic potential in the trap is a convolution (or blur) of the potential at the boundary, such shapes of an electrode interface can provide a higher degree of control over the electrostatic trapping field. Consistent with this principle, strip electrodes can be used. For example, the duty cycle of the strip electrodes could be varied along the longitudinal axis of the ion trap. Such strip electrodes, especially when maintained at different electrical potentials, can define one or more lenses.Using such modulated (wavy or multiply curved) boundaries in this way, especially with strip electrodes, can reduce the number of different non-zero potentials that must be applied to individual electrodes to generate a trapping or confinement field. For example, two different non-zero potentials can easily be used, and with further optimization, this can be reduced to a single non-zero electrostatic potential.

[0019] Fragmentation of ions within the µEST is possible. This can be achieved, for example, by emitting a pulse from a UV or IR laser at the trapping region. The laser can emit the pulse in a direction orthogonal to the long axis (i.e., along the width dimension of the trap). A single laser pulse can be used, timed to match the trajectory of a target ion, or multiple unsynchronized laser pulses can be used. Light-based fragmentation techniques are well known in the art. Their application to a µEST allows the laser emittance to be tuned to fragmentation requirements.

[0020] The µEST can therefore be operated by enclosing one or more precursor ions in the capture region (which can be analyzed and / or selected first), fragmenting the one or more precursor ions, and then detecting the fragmented ions. MS / MS operation is thus possible in both data-dependent (DDA) and data-independent (DIA) acquisition modes. These steps can be repeated to obtain an MS n operation. The use of non-destructive image current detection enables multi-stage analysis of a single ion. Ion fragmentation based on a data-dependent decision is also possible by controlling subsequent fragmentation based on a previous detection.

[0021] In another aspect, an array of microscale electrostatic ion traps (µESTs) can be provided, each ion trap having a longitudinal length of no more than 10 mm and / or at least one electrode (preferably a detection electrode) with a capacitance to ground of no more than 1 pF. Each µEST can therefore analyze a small number of ions, but with a large array, parallel analysis on a large scale is possible. This can improve overall throughput and sensitivity. Optionally, the capacitance to ground of one, some, or each detection electrode(s) is kept low, typically to no more (or less) than 1 pF, 500 fF, 100 fF, 50 fF, 10 fF, 5 fF, or 1 fF.

[0022] The array typically has an inlet for receiving an ion beam, and a portion of the ion beam can be trapped in each of the μESTs. Each μEST of the array typically has a design according to the general details discussed above. As discussed below, such an array may be particularly useful for peptide analysis. The same calibration mixture can be used to calibrate multiple μESTs of the array.

[0023] In particular, the array may have a geometry based on one or more parallel planes, each plane defined by two opposing substrates (wafers) on which electrodes are formed so that they face each other and thereby define one or more µESTs in the same plane. In other words, traps can be formed by using parallel wafers stacked in multiple planes to achieve massively parallel operation. This can be advantageous because a single laser pulse may be capable of fragmenting ions in multiple trapping regions. Additionally or alternatively, three or more substrates may define multiple distinct planes, each with one or more µESTs. If fragmentation is caused by a UV or IR laser, a splitter array can be used to spatially divide the laser pulse output between the different planes.A lens arrangement (particularly using miniature lenses, optionally with anti-reflection coating) can then focus each part of the pulse into a respective collimated beam.

[0024] In operation, ions from a single ion beam can be distributed among multiple µESTs in the array, which can then process the received ions in parallel. Statistical and / or machine learning techniques can be applied to the detection outputs from the µESTs. This can help identify the composition of the individual ion beam. Optionally, a chromogenic tag or a tandem mass tag is used to enhance the analysis.

[0025] Another aspect can be considered in the context of analyzing an ion beam comprising a mixture of different analyte ions. Ions from the ion beam are directed to a plurality of electrostatic ion traps of an array of electrostatic ion traps. Each trap has a longitudinal length of no more than 10 mm (and preferably less, as discussed above) and / or at least one electrode (preferably a detection electrode) with a capacitance to ground of no more than 1 pF (and preferably less, as discussed above). Mass and charge data relating to the ions can then be obtained from the plurality of traps (e.g., by analyzing the ions and / or derivatives of the ions), preferably by at least some simultaneous analysis. The mass and charge data can be combined to identify components of the mixture.This process may be carried out under computer control and implemented in a computer program for execution by a processor configured to control such an array of electrostatic ion traps or a mass spectrometer comprising such an array.

[0026] Advantageously, the ions (and / or their derivatives) can be fragmented in the traps. The precursor ions and / or fragment ions can be analyzed to advantageously obtain mass and charge data from multiple traps and multiple degrees of fragmentation. This MS / MS operation can be extended to an MS by repeated fragmentation. n operation, as discussed above. Other features and / or aspects discussed herein may also be implemented within this approach.

[0027] According to all aspects of the disclosure, higher productivity, higher sensitivity, and higher dynamic range are possible. Combinations of aspects and / or features from aspects are possible. Further advantages can be achieved by combining aspects of the disclosure with ion sorting devices (e.g., ion mobility analysis followed by an ion trap array). BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The disclosure may be put into practice in various ways and preferred embodiments will now be described by way of example only with reference to the accompanying drawings in which: Fig. 1A schematically shows a basic design for a µEST according to one embodiment; Fig. 1B an exemplary distribution of potentials along the z-dimension for the µEST of Fig. 1A shows the injection of ions; Fig. Figure 2A shows a schematic representation of a second embodiment of a µEST in the plane of an electrode set; Fig. 2B the embodiment of Fig. 2A in a vertical plane; Fig. 3A an exemplary signal obtained at the detection electrodes of the µEST of Fig. 2 is induced without noise; Fig. 3B a simulated frequency spectrum of a single positive charge located within the µEST of Fig. 2 oscillates, with thermal noise; Fig. 4 illustrates an exemplary wafer having electrodes formed thereon at various magnification levels and exhibiting an edge roughness of significantly less than 10 nm; Fig. 5 schematically shows a µEST in three consecutive operating steps; Fig. 6A shows a wafer stack comprising a plurality of µESTs; Fig. 6B an enlarged section of Fig. 6A to show ion fragmentation by irradiation according to one implementation; Fig. Figure 7 shows a schematic layout of a wafer and electrical connections for a single row of traps within an array; Fig. Figure 8 illustrates a schematic representation of an experimental setup used for testing and using a µEST arrangement; Fig. Figure 9 schematically illustrates two designs of a planar electrostatic trap electrode, where (a) shows a side view applicable to both designs, (b) shows a top view of a first design with straight (or simply curved) electrode interfaces, and (c) shows a top view of a second design with corrugated electrode interfaces; Fig. 10 illustrates the electrostatic potential along the boundary generated by a sinusoidally varying electrode interface in an example for four different distances from the boundary; Fig. 11 Variations of the electrostatic potential generated by the Fig. 10, as the distance from the electrode increases; Fig. 12 shows different curved electrode interfaces, in particular: (a) a sinusoidal variation of an interelectrode boundary; (b) a square wave interface with curvature of the boundary centerline; and (c) an elongated strip electrode design with modulated duty cycle along the longitudinal axis of the trap. Fig. 13 shows an electrostatic field induced by straight and sinusoidally varying electrode interfaces along the boundary for four different interface lengths; Fig. Figure 14A illustrates an out-of-plane electric field along the centerline of a planar electrostatic trap for an axially offset trap with sinusoidally varying electrode interfaces for four different interface lengths; Fig. Figure 14B illustrates an out-of-plane electric field along the centerline of a planar electrostatic trap for an axially offset trap with rectangular wave varying electrode interfaces for four different interface lengths; Fig. 15 represents a boundary potential due to a square wave type electrode interface; Fig. Figure 16 shows an electrostatic potential resulting from a strip electrode design for four different displacements from the electrode boundary; Fig. Figure 17A illustrates an electrostatic potential of a strip electrode design at (a) the boundary and (b) the centerline for an example with linearly increasing duty cycle; Fig. 17B illustrates an electrostatic potential of a stripe electrode design at (a) the boundary and (b) the centerline for a linearly increasing duty cycle example, where a circular arc in the induced midplane potential is implemented by adjusting the shifting of the duty cycle variation of each stripe; Fig. 18 an electrostatic potential along the centerline of the trap due to the strip electrode design of Fig. 12(c); Fig. Figure 19 illustrates an electrostatic trap design based on electrodes maintained at only two different potentials: (a) boundary potentials of the electrodes for positive voltage electrodes, grounded electrodes, and negative voltage electrodes; (b) a potential induced in the midplane of the trap; (c) a potential along the centerline of the trap. Fig. 20 schematically shows an approach for aligning two substrates of a µEST based on a ball positioned in grooves and Fig. Figure 21 illustrates a schematic structure for an alternative alignment approach in which the surface metallization is deposited on an interlayer dielectric. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0029] The disclosure presents a new type of electrostatic ion trap with a longitudinal length of no more than (and preferably less than) 10 mm. This is referred to as a microscale electrostatic trap (µEST), and in some implementations, the longitudinal length may even be no more than (or less than) 5 mm, 2 mm, or 1 mm. Such an electrostatic ion trap may be formed by a set of planar electrodes, preferably two sets of opposing planar electrodes (parallel to each other). Such electrodes can be reliably formed with nanometer tolerance, for example, using lithographic techniques. A µEST can therefore be adapted for the confinement and / or analysis of small numbers of ions, for example, fewer than 10 or even a single ion. Advantageous designs of µESTs are discussed further herein.

[0030] The use of electrostatic potentials for trapping and / or analysis enables high-resolution analysis for accurate mass determinations. Image current measurement enables non-destructive and reliable detection and even allows detection of individual elementary charges. The latter is facilitated by the small size of the µEST. Indeed, an image current signal V induced by a charge q is proportional to q / C, where C is the capacitance between detection electrodes (which in turn is largely proportional to the size of the detection electrodes). For detection electrodes smaller than 1 mm, this results in an image current signal V in the µV range (i.e., less than 1 mV and usually significantly less than 1 mV, but generally greater than 100 nV).It is advantageous to keep the capacitance of the detection electrodes to ground less than 1 pF, and typically significantly smaller (e.g., 500 fF, 100 fF, 50 fF, 10 fF, 5 fF, or 1 fF). Meanwhile, the noise of modern transistors used to amplify the signal from these detection electrodes could be reduced to well below 10 nV / √Hz. Furthermore, the capacitance of these transistors could also be reduced to below the capacitance C of the detection electrode (or at least on the order of magnitude).

[0031] The inventors have realized that with such a low noise level, it is possible to achieve detections within a time span of 10 ms to 100 ms with an accuracy of charge determination that is better than an elementary charge (e̅=1.602*10 -19Coulomb). This allows not only the mass-to-charge ratio of ions to be determined, but also their charge and thus directly their mass, without having to use, for example, the isotopic distribution. This, in turn, opens up possibilities for high-throughput analysis of individual ions.

[0032] An array of µESTs offers the possibility of analyzing a large number of ions simultaneously without being limited to a single channel and without requiring a large instrument volume. Particularly advantageous µEST designs enable space-efficient arrays and can also enable parallel fragmentation of ions, as described below. An MS / MS and MS n -analysis is also possible.

[0033] The disclosure thus essentially overcomes the problems inherent in the single-channel nature of HR / AM mass spectrometers. The parallel operation of large numbers (e.g., thousands) of μESTs, each with a throughput of 10 to 100 analyses per second, enables new operating modes. For example, such ion storage arrangements allow for the pre-separation of multiple fractions. Higher analysis specificity is also possible.

[0034] This approach differs from known microscale RF traps. These include US8362421, US8835839, Tolmachev et al., Anal. Chem. 86 18 9162-9168 (2014), WO2017062102, US9984861, US8975578, US8841611. Although the dimensions of the ion trap may be similar to those described herein (and some of the fabrication techniques may overlap), the structure of the traps is different, and different voltages are applied.

[0035] With reference first to Fig. 1A, a basic design for a μEST according to one embodiment is schematically shown. The μEST 10 includes a first electrode set 20 and a second electrode set 30. Both the first electrode set 20 and the second electrode set 30 are planar. For example, the first electrode set 20 may include a substrate 22 (e.g., a wafer) and electrodes 25 formed on the substrate 22 (e.g., using lithographic techniques). Similarly, the second electrode set 30 may include a substrate 32 (which may also be a wafer) and electrodes 35 formed on the substrate 32. The electrodes 25 and the electrodes 35 are elongated in a plane perpendicular to that of the drawing (in other words, they extend in a width dimension). The height, and sometimes also the width, are typically smaller (and preferably significantly smaller) than the length.The use of two opposing sets of electrodes D can provide a high quality of the electric field.

[0036] Also shown is a longitudinal axis 40 of the µEST 10 (which can be considered defining a "z" dimension). The electrodes 25 and the electrodes 35 can therefore be considered to be distributed along the longitudinal axis 40, with their width dimension (along an "x" axis) thus being perpendicular to the longitudinal axis 40 (and not entirely in the plane of the drawing). As stated above, a maximum length of the µEST 10 along the longitudinal axis 40 is no more than 10 mm, preferably no more than 2 mm, and more preferably no more than 1 mm. The distance between the two sets of electrodes 20, 30 defines a height dimension (along a "y" axis) that can be adjusted through the use of precision spacers (not shown).

[0037] Electrodes 25 and electrodes 35 each have a corresponding function, with opposing electrodes of the first electrode set 20 and the second electrode set 30 having the same function. The two middle electrodes D are used for ion detection. At least some of the electrodes are configured to receive an electrostatic potential to confine received ions. The outermost electrodes R are used for ion reflection (ion mirrors), and a suitable DC potential is applied to them. The electrodes between the detection electrodes D and the reflection electrodes R are acceleration electrodes A, to which a suitable electrostatic potential is applied to accelerate the ions and spatially focus them.An exemplary ion trajectory 45 is shown in which the ions are confined in a capture region of the µEST 10 formed in the distance between the first electrode set 20 and the second electrode set 30.

[0038] Next, referring to Fig. Figure 1B is an example distribution of potentials along the z-dimension for the µEST of Fig. 1A for ion injection. In this mode of operation, a voltage at the trap entrance (applied to the reflection electrodes R) is reduced to admit a short packet of ions of interest (which can optionally be preselected with respect to mass). The voltage applied to the reflection electrodes R is then raised to a reflection level before ions return to the entrance to provide a trapping mode. In Fig. 1A, the injection is shown from above along the z-axis. After the voltage applied to the reflection electrodes R has been increased (so that the trap is closed) and the ion trajectory has been stabilized, detection is performed using the detection electrodes D. An on-chip differential amplifier 50 receives the image current from the detection electrodes D. The resulting signal is passed towards multiplexing and signal processing electronics, some of which may be located off-chip. For example, some of the signal processing could also be implemented on the same circuit logic, while a remaining part (or parts) of the signal processing is (are) performed on an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA).

[0039] Detection is thus non-destructive based on an image current, and therefore multiple stages of mass analysis become possible, as discussed below. The small size of the trap (with a typical inter-electrode spacing of less than 50 to 100 µm) allows for significantly lower capacitance of the detection electrodes than in existing electrostatic traps. This enables single-charge sensitivity and also allows for the simultaneous measurement of both the charge and the mass-to-charge ratio of individual ions. In this respect, the electrostatic trap can be considered similar to, for example, a cone trap as described in DZ Keifer, EE Pierson, MF Jarrold, Analyst 142, 1654 (2017), but exhibits much higher sensitivity and greater independence of the oscillation period on the initial parameters of the incident ions.

[0040] Using a trap scaled to sub-millimeter dimensions (as in Fig. 2), yields oscillation frequencies in the range of approximately 1 to 10 MHz. This allows resolutions in the range of 30,000 to 100,000 with less than 20 ms measurement time for a peptide ion acceleration of 100 to 200 V. For this purpose, a mean free path of more than 100 m with a vacuum of less than 10 -7 mbar (10 -5 (Pa). It is understood that the frequency dispersion, and thus the accuracy of the mass determination of the ions of interest, is related to the design tolerance (flatness, parallelism, line accuracy, etc.). The exact relationship may depend on the beam and the optics.

[0041] In the general sense of the disclosure and according to one aspect, an electrostatic ion trap may be considered, comprising: a first set of planar electrodes distributed along a longitudinal axis of the ion trap; and a second set of planar electrodes distributed along the longitudinal axis of the ion trap, wherein each of the electrodes of the second set is arranged to be spaced from and opposite a corresponding electrode of the first set. A length of the first and second sets of planar electrodes along the longitudinal axis is advantageously no more than 10 mm (and optionally no more than 5 mm, 2 mm, 1 mm, or 0.5 mm). Additionally or alternatively, a capacitance of at least one of the electrodes (preferably one, some, or each detection electrode(s)) to ground is no more than 1 pF.Advantageously, at least some of the electrodes of the first and second sets are configured to receive an electrostatic potential to confine ions received in the space between the first and second sets of planar electrodes. The electrostatic ion trap may be configured to receive no more than 100 (optionally 50, 40, 30, 20, 10, or 5) ions injected into the electrostatic ion trap, and preferably, the electrostatic ion trap is configured to receive a single ion injected into the electrostatic ion trap. A controller and / or processor may be provided to control the operation of the electrostatic ion trap and / or to receive one or more outputs from the electrostatic ion trap.A computer program comprising instructions for implementing a method of operation described herein may be configured to operate on such a processor.

[0042] A corresponding method for manufacturing and / or operating such an electrostatic ion trap may also be contemplated (e.g., including a method for analyzing an ion beam), comprising steps for forming and / or providing and / or using the features of this device. For example, the first and second sets of electrodes may be fabricated using lithographic techniques.

[0043] Preferably, at least one of the electrodes (and more preferably some of the electrodes) is (are) a detection electrode configured to detect an image current of trapped ions. By using such a small electrostatic trap size (as discussed above), detection of image currents with a resolution better than 1 elementary charge is possible. The detection electrode or electrodes may be located towards the center of the ion trap along the longitudinal axis. The capacitance of one, some, or each detection electrode(s) to ground is advantageously kept low, typically to no more than 1 pF, 500 fF, 100 fF, 50 fF, 10 fF, 5 fF, or 1 fF. This may also be implemented and / or advantageous without a longitudinal length of no more than 10 mm, although the parameters may be closely related.

[0044] In one embodiment, some of the electrodes are reflective electrodes configured to receive a reflective potential. The reflective electrodes are advantageously located at the ends of the ion trap along the longitudinal axis. In embodiments, the potentials at the reflective electrodes are selectively configured to be: at a lower level to allow ions to enter the ion trap; and at a higher level to confine the ions within the ion trap.

[0045] Optionally, some of the electrodes are acceleration electrodes configured to receive an acceleration potential. The acceleration electrodes are preferably located between the reflective electrodes and the detection electrodes along the longitudinal axis.

[0046] Advantageously, the first set of electrodes is formed on a first planar substrate. In embodiments, the second set of electrodes is formed on a second planar substrate opposite the first planar substrate. The first and second substrates may form part of an integrated circuit. A distance between adjacent electrodes is preferably no more than 500 µm, 200 µm, or 100 µm (and more preferably no more than 50 µm). One or more spacers may be provided between the first and second sets of electrodes. This may define a height of the device.

[0047] In embodiments, the arrangement of the first set of electrodes is substantially symmetrical between opposite sides of a center of the electrostatic trap along the longitudinal axis. Additionally or alternatively, the arrangement of the second set of electrodes is substantially symmetrical between opposite sides of a center of the electrostatic trap along the longitudinal axis.

[0048] The electrostatic ion trap can be configured so that one or more of the following applies: a measurement time is not more than 20 ms; an acceleration voltage is not more than 200 V and a gas pressure in the electrostatic ion trap is not more than 10 -7 mbar.

[0049] Details of specific embodiments will now be discussed. Further description in accordance with this general spirit and other general spirits of the disclosure is provided below.

[0050] In practice, more complex electrode configurations than those in Fig. 1A to provide more optimized µEST characteristics with reduced spatial and time-of-flight deviations. In this regard, the next point will be Fig. 2A, which is a schematic representation of a second embodiment of a µEST in the plane of an electrode set (using the method described with reference to Fig. 1A, xz-plane, y=0). It is also shown on Fig. 2B, which shows the embodiment of Fig. 2A in a vertical plane (yz-plane, x=0). Both Fig. 2A as well as Fig. 2B are labeled with dimensions, all given in mm, and further labeled with stresses (stresses and dimensions are rounded to the nearest digit).

[0051] The Fig. 2A and Fig. The design shown in Figure 2B differs in a number of aspects from that shown in Fig. 1A. First, a larger number of electrodes are provided, including a central electrode E0 between the central detection electrodes (D1, D2). Second, the shape of the electrodes differs. The electrodes on one side of the line z=0 have a generally rectangular shape (in the xz plane), while the electrodes on the other side of the line z=0 have shapes defined by arcs. The central electrode E0 has an edge on one side of the line z=0 defined by a straight line and an edge on the other side of the line z=0 defined by an arc. This central electrode E0 functions as a curved lens, with some of the other curved electrodes having a mirror function. Nevertheless (and as can be seen from Fig. 2B), the arrangement of the electrodes on both sides of the line z=0 is otherwise symmetrical. As in Fig. As shown in Figure 2B, the distances between all electrodes are 0.005 mm.

[0052] The arc-defined edge of the central electrode E0 and the adjacent edge of the detection electrode D1 are both defined by concentric circles centered at z=-1. The radius of the edge of the detection electrode D1 is indicated as R1. The edges of all other electrodes on this side of the line z=0 (except the far edge of the end electrode) are defined by concentric circles centered at z=+5.3. The radius of the edge of the sixth electrode, closest to the line z=0, is also indicated as R6. The central electrode or curved lens E0 and the curvature of the electrodes in the z<0 part of the design (left side) keep the ions along the z-axis. Otherwise, the ions could drift in the x-direction (along the width of the trap). Additionally, the curvature of the central electrode or the curved lens E0 can compensate for TOF deviations from the curvature of the electrodes on the left side.This curvature can allow for ion confinement in the X direction, preferably well within the X dimension of the detection electrodes D1 and D2. Instead of a curvature, additional electrodes could be placed above and below . Fig. 2A can be used (not shown), which provide such containment by edge fields.

[0053] The DC voltages applied to the electrodes are also shown. These voltages are applied symmetrically to electrodes on either side of the line z=0 and also symmetrically to opposite electrodes of the two sets, with the exception of the potential U0 applied to the central electrode E0, for which an opposite offset (labeled ±Δ) is applied to the opposite electrodes for tuning.

[0054] Symmetry of the power supply electrodes with respect to each trap is desirable (these are not shown, but are usually adjacent to the far edges of the shown electrodes in the x-dimension and extend in the z-dimension), at least where the trap width in the x-dimension (width) is no more than 8 times h (where h is the height of the trap in the y-dimension, in this example 60 µm). Otherwise, uncompensated ion drift in this direction could occur, which could corrupt the time of flight. This may be particularly relevant in a variant implementation where only electrodes without curvature are used (such as on the right side of Fig. 2A, where z>0, and mirror image on the left). In this case, fringing fields can be used to limit ion motion along the x-dimension.

[0055] The Fig. 2A and Fig. The configuration shown in Figure 2B thus demonstrates a more advanced planar µEST geometry that confines ions in all directions while providing a resolving power of up to 100,000 (or a mass accuracy of less than 10 ppm) for ions with an energy spread of + / -1% within an incoming beam occupying 40% of the interelectrode spacing. This geometry can be considered a combination of planar electrostatic mirrors with curved mirrors and a curved cylindrical lens at the center.

[0056] During operation, ions oscillate between the electrodes receiving the U6 potential. The electrode receiving the U2 potential is the accelerating electrode. The electrodes receiving the U3, U4, and U5 potentials are fine-tuned to reduce or minimize higher-order deviations in both spatial and time-of-flight focusing. This potentially enables mass resolution one or more orders of magnitude higher than with the design of Fig. 1 is possible. In addition, sophisticated ion focusing properties, such as a weak dependence on ion energy, angular spread and / or beam size, are possible.

[0057] Now with reference to Fig. Figure 3A is an example signal obtained at the detection electrodes of the µEST of Fig. 2 is shown without noise. It is also shown on Fig. 3B, in which a simulated frequency spectrum of a single positive charge located within the µEST of Fig. 2, with thermal noise. These diagrams demonstrate the highly anharmonic nature of the oscillations, resulting in the first and third harmonics of the signal having similar amplitudes. Consequently, each ion could be detected at one or both of these frequencies, advantageously with a signal-to-noise ratio high enough to determine its charge from both harmonics. Such a signal could be obtained using low-capacitance JFET transistors wire-bonded to the wafer (substrate) or transistors fabricated with the wafer in a single CMOS process. If the upper and lower wafers are separated by precision spacers, the first amplification stage can occur on one or both wafers.A deviation between the separation spaces provided by spacers for the same trap is preferably less than 5%, 2%, 1%, and most preferably exactly or no more than 0.5% or 0.2% of the ion beam size (e.g., the largest cross-sectional dimension, which in this example is about 40% of the inter-wafer spacing, h). If the beam size is unknown, this range may correspond approximately to at least 0.1% and no more than 2% of the inter-wafer spacing (h). For the trap sizes contemplated in this disclosure, this may correspond to a parallelism of 0.1 µm to 1 µm.

[0058] In an advantageous implementation, opposing detector plates can be connected by precision conductive spacers. These can be patterned using MEMS processes, for example, near the sensitive areas. In this case, one readout circuit can be used for a single detector cell. If non-conductive spacers are used, two separate readout circuits may be required for the upper and lower substrates of a single detector cell. In this case, the signals can be added electrically after amplification.

[0059] High resolution and mass accuracy can be achieved by high-order time-of-flight focusing within the electrostatic trap combined with nanometer-scale fabrication accuracy on a planar wafer. With reference to Fig. Figure 4 illustrates an exemplary wafer having electrodes formed thereon at various magnification levels and showing an edge roughness of significantly less than 10 nm. This is easier to achieve when the metallization is very thin, for example, about 75 nm, as in Fig. 4. High accuracy of edge definition by lithographic techniques can determine the ion optical quality of the µEST as well as the final mass accuracy and mass resolution. In general, a ratio of the inter-wafer spacing size to an accuracy of edges of inter-electrode spacings (in particular between the reflective electrode R and the accelerating electrode A and / or between the accelerating electrode A and the detecting electrode D) should be at least 1000, preferably at least 2000, 5000, or 7000, and most preferably at least or greater than 10000, 20000, or 50000. It is also desirable that both wafers are well aligned, in particular within at most 2% of the ion beam size and preferably within at most 0.5% of the ion beam diameter (which, in the example of the disclosure, is about 40% of the inter-wafer spacing, h).For the trap sizes considered in this disclosure, this corresponds to an alignment accuracy of 0.1 µm to 1 µm.

[0060] A mass accuracy in the range of several parts per million could make it possible to narrow down the list of possible compounds (e.g., peptides in bottom-up proteomics) from existing databases.

[0061] Returning to the general spirit of the disclosure discussed above, further optional features may be considered. For example, one or both edges of at least some of the electrodes (on a side of the electrode extending perpendicular to the longitudinal axis, i.e., in the width dimension) may have an arc shape (and optionally, both edges may have arc shapes defined, for example, by the same circle, or the edges may have arc shapes defined by different circles). Additionally or alternatively, at least some of the electrodes may have a curved shape, an arc shape (this may be applied, for example, to reflective electrodes), or a circular or elliptical shape (for example, applied to detection electrodes, which may be based on two circular arcs).This may only apply to electrodes on one side of a center of the electrostatic trap along the longitudinal axis (line z=0).

[0062] A central electrode may be provided between the central detection electrodes. The central electrode may be configured to act as an ion lens. Preferably, the central electrode has at least one curved edge (in the width dimension).

[0063] In embodiments, a transistor (e.g., a FET or JFET) is connected to the detection electrode (or electrodes). Advantageously, the transistor may be formed by lithographic techniques and / or form part of the integrated circuit. Preferably, the transistor is wire-bonded to the substrate or integrated into it, e.g., by a CMOS manufacturing process. A capacitance of the transistor is preferably comparable (e.g., within an order of magnitude) to a capacitance between detection electrodes and / or the capacitance between a detection electrode and ground.

[0064] If one or more spacers are provided between the electrode sets, at least one of the one or more spacers may be conductive to couple at least one electrode on the first electrode set to at least one electrode on the second electrode set (e.g., detection electrodes of each set). A parallelism of the spacers of 0.1 µm to 1 µm is preferred.

[0065] In some implementations, ions can be selected by applying a pulsating voltage to one of the reflective electrodes, causing at least some ions (e.g., unwanted ions) to leave the trap.

[0066] Advantageously, a ratio of the spacing size between planar substrates to an accuracy of edges of a spacing between adjacent electrodes of the first set and / or the second set is at least 1000, preferably at least 2000, 5000 or 7000 and most preferably at least or greater than 10000, 20000 or 50000. Additionally or alternatively, an alignment of the planar substrates may be within an accuracy of 0.1 µm to 1 µm.

[0067] Further specific details are discussed again before returning to the general meaning of Revelation.

[0068] Fragmentation of ions in a µEST is possible by irradiation techniques that can be adapted to the planar geometry of the µEST. Next, referring to Fig. Figure 5 schematically depicts a µEST in three consecutive operational steps: a) precursor analysis; b) selection and fragmentation; and c) fragment analysis. This represents a simple form of multi-step analysis. In step a), the ion trajectory 45 is a normal inclusion pattern, as described above with respect to Fig. 1A. This enables analysis of precursor ions. In step b), the ion trajectory 46 is influenced by irradiation with a focused ultraviolet (UV) or infrared (IR) laser pulse until the ion fragments form (as discussed below). The resulting fragments continue an inclusion trajectory 48 in the µEST and are analyzed again in step c). Repeating steps b) and c) enables MS n -Operation.

[0069] UV photodissociation is frequently used in conventional mass spectrometry (see, for example, WO-2007 / 109672). Advantageously, it could be used to provide additional structural information about ions within µESTs. Ions of interest could optionally be selected in step b) by pulsing down a voltage applied to an upper reflective electrode of the µEST to allow all unwanted ions to leave the trap (by the pulse voltage added to U6 in Fig. 2A). When an ion of interest reaches an inflection point 47, it is exposed to a focused UV light pulse (for example, from a 213 nm Nd:YAG or a 193 nm ArF laser). For better selectivity, the timing of the UV pulse could be adjusted to the trajectory of the target ion. Alternatively, the timing could be unsynchronized, but then multiple pulses could be used to increase the irradiation probability of the ion of interest (preferably to 100%). A UV laser pulse of a few nanoseconds duration can easily produce fragmentation of most biologically relevant organic molecules (see, for example, J.S. Brodbelt et al., Chem. Rev. 120, 3328 (2020)). IR can be used instead of UV. As stated above, the selection and fragmentation process could be repeated several times (MS napproach), for example, depending on the probability of formation and capture of charged fragments. Fragmentation at the inflection point can offer the advantage of minimizing the initial energy of fragment ions, thereby reducing energy dispersion and improving analytical accuracy.

[0070] Reconsidering the general spirit of the disclosure, other advantageous features may be contemplated. For example, the electrostatic ion trap may further comprise a UV or IR laser configured to emit a pulse at a trapping region of the electrostatic ion trap to thereby fragment ions trapped in the trapping region. Advantageously, the laser may be configured to emit the pulses in a direction orthogonal to the longitudinal axis of the electrostatic ion trap. In some embodiments, the laser is configured to emit a single laser pulse whose timing is synchronized with a trajectory of a target ion. Alternatively, the laser may be configured to emit multiple laser pulses that are not synchronized with a trajectory of a target ion.

[0071] The laser can be controlled to fragment ions in the capture region. The controller or processor can then receive a signal from the detection electrodes to detect ions fragmented in the capture region. Preferably, additional ion detection and / or selection is performed prior to fragmentation.

[0072] Another fragmentation embodiment could include the same UV laser used to illuminate the surface of electrodes 22 to emit electrons via a photoelectric effect. This could enable other general electron dissociation (ExD)-type fragmentation processes, such as electron capture dissociation (ECD), electron-induced dissociation (EID), etc. A weak magnetic field from external permanent magnets could be added to increase the residence time of electrons in the trap and thus the fragmentation efficiency.

[0073] In preferred implementations, the electrostatic ion trap can be controlled to cause repetition of fragmentation and detection. This allows MS n Operation in the electrostatic ion trap can be provided. Optionally, fragmentation can be controlled in response to information determined from a previous detection. In this way, ion fragmentation can be effected based on a data-dependent decision.

[0074] Additional details of specific embodiments are again discussed before further discussing the general spirit of the disclosure.

[0075] The design of a µEST on a small scale, and in particular on a substrate, such as a wafer, allows the placement of a respective set of electrodes for each of a plurality of traps on a single wafer. By using two such wafers, a two-dimensional array of traps can be created. Using three or more wafer stacks at multiple levels can thereby provide multiple such two-dimensional arrays and enable a three-dimensional array of µESTs. In this way, a large number of µESTs can be provided within a small volume, enabling massively parallel operation.

[0076] Next, referring to Fig. 6A shows a wafer stack comprising a plurality of μESTs. Each of the wafers may have electrodes formed on both the top and bottom surfaces, as discussed above. Stack 80 includes a first wafer 81 and an adjacent second wafer 82 separated by a height of 50 μm.

[0077] It will now Fig. 6B, which shows an enlarged section of Fig. 6A to show ion fragmentation by irradiation according to one implementation. Multiple ion confinement regions 100 are illustrated, each defined by a respective μEST comprising individual electrodes formed on the wafers. Ions enter each of the μESTs along axes 110 from the edge of wafers (which are also long axes of each μEST). Thus, N μESTs can be provided in a single row. A laser pulse 120 is directed along the plane of ion confinement in a direction perpendicular to the axes 110 of ion entry. In this way, a single laser pulse 120 can be used to fragment ions in multiple μESTs simultaneously.

[0078] With an array of N traps arranged in a row with M rows stacked on top of each other, a single laser pulse could be split into M sub-beams, each focused into a collimated beam by an array of miniature lenses with anti-reflection coating. With N=10 to 20, the traps are 5 to 10 mm, and the beam diameter could be maintained within the required 20 to 30 µm along this entire length and without contacting electrodes. To achieve this, the angular divergence should be within approximately ±1 mrad. With a fragmentation threshold for peptides of 1 mJ / mm 2 less than 1 µJ pulse energy per row may be required, but with tight collimation.

[0079] Next, Fig. 7, which shows a schematic layout of a wafer for a single row of traps within an array. Eight traps are shown, comprising: a first trap 131; a second trap 132; a third trap 133; a fourth trap 134; a fifth trap 135; a sixth trap 136; a seventh trap 137; and an eighth trap 138. Each of these traps is spaced apart from one another, preferably by a distance of at least (or more than) 6 h between their long axes, most preferably by a distance of at least (or more than) 10 h, where h represents the spacing between wafers (in other words, the height of the trap). Since fringe fields reduce exponentially upon movement away from the long axis of the trap, a value of at least about 3 h away from the ions on the z-axis is unlikely to affect the field.For these reasons, transistors for image current detection, wires or similar can be placed in this way.

[0080] In Fig. 7 also shows wires for connecting to the traps. In particular, DC voltage wires 141, 142, 143, 144, 145, and 146 provide DC voltages to and between the traps (smaller, similar connecting wires are provided between adjacent traps, but these may not be clearly visible in the drawing). Pulsed signal wires 151, 152, 153, 154, 155, and 156 provide pulsed signals to the traps (similar wires for providing pulsed signals to other traps are present but not highlighted). Output signal lines 160 (connected to the drain and source of the detection JFETs) are also indicated.

[0081] According to standard notation for mass spectrometry (see, for example, P. Roepstorff, J. Fohlman, Biomed. Mass Spectrom. 11(11), 601(1984)), most UVPD fragments for tryptic peptides are a- and y-ions, followed by x- and z-species. Low-energy charged fragments formed during this pulse are typically accelerated from the inflection points back to the µEST, while uncharged fragments and unselected precursors are lost during analysis. After detection of charged fragments in the µEST and their accurate mass measurement, important structural information (sequence tags) about the ion of interest can be derived to determine the correct compound (e.g., a peptide) over candidates from a library that can be shortlisted after filtering by precursor mass.

[0082] For MS / MS and MS napproaches using µESTs, a modification of the existing tools used in conventional mass spectrometry may be desirable. First, increased ambiguity may be caused by the presence of only one isotope in the spectrum, leading to an unknown isotopic abundance (for example, at 13 C or 15 N). With multiple traps and higher throughput, the identification process can benefit significantly from the application of statistical and / or machine learning techniques. The use of chromogenic tags attached to peptides can also be considered to increase the identification rate. TMT and TMTPro reporter ions could be used to analyze grouped samples.

[0083] The output of each µEST in an array can be individually digitized and processed. This allows mass / intensity pairs to be extracted. Intensities can be converted into an integer number of charges (charge state) of the ion. This allows mass determination from an m / z measurement with low ppm accuracy. Data from MS / MS and / or MS n can be linked to the single-level (MS) data of the predecessor. This data can then be used for a search (e.g., in a database).

[0084] Only one isotopologue is likely to be detected per trap. Furthermore, the average number of fragments is typically lower than with conventional (macroscale) mass spectrometry. Therefore, the search space for all output data is generally broader than with conventional proteomic analysis. In contrast, the ability to directly link fragments to precursors (since the precursor is a single ion) can reduce the search space compared to macroscale proteomic analysis. Data from other traps could also be considered to better identify precursors, for example, using machine learning.

[0085] µEST can be useful even without fragmentation. This can be useful, for example, when a given sample can exhibit different charge states at the same mass-to-charge ratio (m / z), such as in intact protein analysis and top-down proteomics.

[0086] In a general sense of the disclosure (which may be combined with, or be part of, the general senses discussed above), an array of electrostatic ion traps may be considered, wherein each ion trap has a longitudinal length of no more than 10 mm and / or wherein at least one electrode (preferably one, some, or all of the detection electrode(s)) has a low capacitance to ground of generally no more than 1 pF (and optionally lower, as indicated above). The longitudinal length may optionally be no more than 5 mm, 2 mm, 1 mm, or 0.5 mm. Advantageously, the array comprises an inlet for receiving an ion beam configured such that a portion of the ion beam can be trapped in each of the ion traps. A controller and / or processor may be provided to control the operation of the array and / or to receive one or more outputs from the array.Furthermore, a corresponding method for manufacturing and / or operating such an arrangement of electrostatic ion traps may also be considered, comprising steps for forming and / or providing and / or using the features of this device.

[0087] In one aspect, a method for analyzing an ion beam comprising a mixture of different analyte ions may be contemplated. The method comprises: directing ions from the ion beam to a plurality of electrostatic ion traps of an array of electrostatic ion traps (e.g., the array as discussed above and elsewhere herein, optionally including any features of the electrostatic ion traps described herein), each electrostatic ion trap having a longitudinal length of no more than 10 mm; obtaining signals indicative of mass and charge data relating to the ions from the plurality of electrostatic ion traps; and combining the mass and charge data obtained from the signals to identify components of the mixture. The ion beam may be generated from a mixture of analytes.

[0088] The signals are advantageously obtained by analyzing the ions and / or derivatives of the ions. For example, the ions or their derivatives in each trap can be considered precursor ions. Then, the precursor ions in the multiple traps can be fragmented to obtain fragment ions. Obtaining signals can include obtaining signals by analyzing the precursor ions in the multiple traps and / or obtaining signals by analyzing the fragment ions in the multiple traps. Combining the mass and charge data can then combine mass and charge data related to the precursor ions and / or mass and charge data related to the fragment ions. Advantageously, the steps of fragmenting, obtaining signals, and combining the mass and charge data are repeated sequentially (to generate an MS n -operation).

[0089] Obtaining signals may involve simultaneously analyzing ions in each of the multiple traps. This may include simultaneously analyzing a set of ions in the multiple traps and / or simultaneously analyzing fragment ions in the multiple traps. Simultaneous fragmentation of ions in the multiple traps is also possible.

[0090] In accordance with this method aspect (and any other method aspect provided herein), a computer program may be provided comprising instructions that, when executed by a processor, cause the processor to perform the corresponding method. For example, the processor may be configured to control an array of electrostatic ion traps (or a mass spectrometer comprising such an array). A (non-transitory) computer-readable medium comprising or having such a computer program stored thereon may also be provided.

[0091] Various options are now contemplated according to any of the above aspects and / or implementations. For example, each electrostatic ion trap may be (and preferably is) according to any of those described above. For example, the electrostatic ion trap may comprise: a first set of planar electrodes distributed along a longitudinal axis of the respective ion trap; and a second set of planar electrodes distributed along the longitudinal axis of the respective ion trap, each of the electrodes of the second set being arranged to be spaced from and opposite a corresponding electrode of the first set.A length of the first and second sets of planar electrodes along the longitudinal axis is no more than 10 mm, and / or at least one electrode (preferably a detection electrode) may have a capacitance to ground of no more than 1 pF (and optionally less, as identified herein). At least some of the electrodes of the first and second sets may be configured to receive an electrostatic potential to confine the ions received in the space between the first and second sets of planar electrodes.

[0092] In preferred embodiments, the array is configured with multiple electrostatic ion traps in the same plane. Additionally or alternatively, multiple electrostatic ion traps may be provided in different planes. If multiple electrostatic ion traps are provided in the same plane, a single laser pulse can be used to fragment ions in multiple electrostatic ion traps (in particular, their respective trapping regions) in that plane. A single laser pulse can also be used to fragment ions trapped in different planes. For example, a UV or IR laser may be provided, configured to generate a pulse. A splitter array may then be configured to spatially divide the generated pulse into parts and direct each part along a respective different plane.A lens arrangement comprising a plurality of (miniature) lenses may be used. Each lens is advantageously configured to focus a respective portion of the generated pulse into a respective collimated beam. An anti-reflection coating may be applied to the lenses.

[0093] Ions can be collected from a single ion beam in multiple electrostatic ion traps of the array. The ions collected in the multiple electrostatic ion traps can be processed in parallel (especially if the ion beam includes ions from a peptide).

[0094] Detection outputs from each of the plurality of electrostatic ion traps may be provided to a processor. The processor may then be configured to apply statistical and / or machine learning techniques to the detection outputs to identify a composition of the individual ion beam.

[0095] To calibrate the multiple electrostatic ion traps, ions from the same calibration mixture can be injected into multiple electrostatic ion traps of the array.

[0096] An ion beam may be transmitted to at least one electrostatic ion trap of the array, wherein the ion beam includes at least one ion with a chromogenic tag or a tandem mass tag.

[0097] Additional details of specific embodiments are again discussed before further discussing the general spirit of the disclosure.

[0098] Next, referring to Fig. Figure 8 illustrates a schematic representation of an experimental setup used to test a µEST assembly. This includes: an existing macroscale mass spectrometer 200 (sold by Thermo Fisher Scientific, Inc. under the name Orbitrap™ Exploris™ 480) as the front-end device; an adapter chamber 300; and a µEST assembly 400. The macroscale mass spectrometer 200 includes: a high-capacity transfer tube 210; an electrodynamic ion funnel 220; an internal calibration source 230; an active beamguide 240; a quadrupole mass filter 250; an ion gate 260; a curved ion trap (C-trap) 270; an orbital trap mass analyzer 280; an ion guide multipole 290; and a transport multipole 295.

[0099] The adapter chamber 300 includes: a shut-off valve 310; an ion funnel 320 with a gas line 325; a Z-lens (line-of-sight blocker) 330; an X, Y deflector 340; and lenses 350.

[0100] Before analytical runs, each µEST can be calibrated using the same calibration mixture as the front-end instrument. During operation, the mass spectrometer's internal calibrant from Source 230 can be used to monitor the mass accuracy of each trap within the array and can be used as a locking mass if necessary.

[0101] In operation, each µEST is filled sequentially (although parallel filling is possible), for example, in a grid. This can be achieved by pulsing the reflecting electrode to receive an ion with a specific m / z ratio (as described above with respect to Fig. 2, where the impulse is added to the U6 potential). Each µEST can thus (due to its small size) be used to detect a single charge.

[0102] Single-ion sensitivity, even at high repetition rates, allows µESTs to measure even species with very low abundance within a mixture. This, in turn, could enable deeper proteome coverage or similar. On the other hand, the small size of the µEST, which enables such highly sensitive detection, may also limit the number of analyzed ions to a maximum of a few dozen per injection.

[0103] Alternative designs for planar electrostatic ion traps based on modulated or corrugated interfaces between adjacent electrodes are now also being considered. These are applicable to and / or combinable with any other design or implementation disclosed herein. A corrugated interface between a pair of electrodes maintained at different potentials can have the effect of smoothing the transition between the potential ranges compared to the case of a straight electrode and can provide improved control over the electrostatic field confining the ions. This design may also potentially allow ion traps to be tuned for higher performance and reduce the required number of electrodes with different potentials.Additionally, these designs can help reduce the sensitivity of trap performance to electrode plate misalignment. This can be particularly important during the assembly and operation of µESTs.

[0104] Next, referring to Fig. Figure 9 schematically shows two designs of a planar electrostatic trap electrode, where (a) shows a side view applicable to both designs, (b) shows a top view of a first design with straight (or simply curved) electrode interfaces, and (c) shows a top view of a second design with corrugated electrode interfaces. The design in Fig. Figure 9(b) is a planar electrostatic trap design based on straight electrode interfaces, as seen for: a first set of electrodes 301; a central electrode 302; and a second set of electrodes 303. As discussed above, the electrodes are held at carefully selected potentials to generate a trapping field, while the recording electrodes measure the image charge induced by the ion. The trap axis is indicated by the dashed line along the z-axis.

[0105] As from Fig. As shown in Figure 9(a), a planar electrostatic ion trap comprises two opposing electrode plates. As discussed above, each electrode is held at a fixed potential, and the combined electrostatic field of the electrodes confines the ion. In a multi-reflective design, ions are introduced by lowering and raising a gate electrode along the trap axis. Ions are then reflected between a pair of electrostatic mirrors at each end of the trap, confining the ions for multiple cycles and allowing accurate measurement of the oscillation frequency.

[0106] The accuracy of mass-to-charge ratio prediction can be limited by the variation in ion oscillation frequency (or equivalently, time-of-flight) depending on ion energy, insertion angle, and position. Therefore, to improve (or potentially maximize) the accuracy of mass-to-charge ratio prediction, the geometry and potential of each electrode are optimized to minimize time-of-flight variation due to uncontrolled experimental sizes.

[0107] Conventional designs for planar electrostatic ion traps are based on electrode sets with uniform boundaries along the transverse axis of the trap (which in Fig. 9 is the x-axis). The potentials and lengths of the electrodes can then be carefully chosen to minimize the variation in time of flight for trajectories closely aligned with the trap axis. This optimization can be performed by applying a Taylor expansion for the time of flight around the main trajectory and minimizing the Taylor series coefficients (often called deviation coefficients) with respect to ion energy, angle, and position. This process can be continued to the highest order possible until the degrees of freedom offered by the electrodes are no longer sufficient to continue. To obtain additional degrees of freedom in this optimization process, more electrodes can be added, but constraints on the minimum electrode size and the number of required voltage supplies can quickly become a problem.

[0108] With reference to Fig. Figure 9(c) shows a planar electrostatic trap utilizing corrugated electrode interfaces and strip electrodes. As can be seen, the first electrode set 311 comprises a high potential electrode 311a and a negative potential electrode 311b with a corrugated interface therebetween. Similarly, the central electrode 312 comprises a high potential electrode 312a and a negative potential electrode 312b with a corrugated interface therebetween, and the second electrode set 313 comprises a high potential electrode 313a and a negative potential electrode 313b with a corrugated interface therebetween. Grounded pickup electrodes 315 are also shown. This design thus utilizes electrodes maintained at only three different potentials: high potential, negative potential, and grounded.

[0109] This approach extends planar electrostatic trap designs by curving the interfaces between adjacent electrodes. Specifically, corrugated interfaces are introduced between adjacent electrodes. This effectively smooths the transition between potential regions at the boundary. This is possible because the electrostatic potential in the trap is a convolution or blurring of the potential at the boundary. Using electrode interfaces of arbitrary geometry can therefore provide a higher degree of control over the electrostatic trapping field.

[0110] Designs that utilize these so-called corrugated electrodes can offer several advantages compared to designs with straight electrode geometries. First, because each electrode provides greater control over the electrostatic field, fewer electrodes may be required to achieve the same level of trapping performance. This can be particularly desirable when designing and building large µEST arrays, as fewer connections to external power supplies are required.

[0111] Planar electrostatic ion traps can also be sensitive to misalignment of the electrode plates, particularly relative displacements along the trap axis. This sensitivity can be caused by the strong changes in the electrostatic field along the axis. If the electrode plates are not precisely aligned, an unbalanced electric field can be generated, which can force ions out of the plane of the trap (which is Fig. 9 is the xz-plane). Wavy electrode interfaces can smooth the sharp transitions in the electrostatic field resulting from this misalignment and reduce the strength of the resulting out-of-plane electric field (which is Fig. 9 is the y-axis). The high tolerances required for optimal ion trap performance can make the construction and alignment of electrode plates for µEST challenging. Therefore, corrugated electrode interfaces may be ideal for this application.

[0112] The electrostatic fields generated by corrugated and straight electrode interfaces can be compared, as will now be discussed. It is evident that small-scale interface features are rapidly suppressed with increasing distance from the interface. Furthermore, the gradient of the electrostatic potential within the trap can be precisely controlled by varying the electrode interface. It can also be observed that corrugated electrode interfaces generate smaller out-of-plane electric fields (those in Fig. 9 are the y-axis) when the electrode plates are misaligned.

[0113] The electrostatic field within the trap is determined by the potential along the region boundaries. If a designer were able to continuously vary the potential across this boundary, any desired electrostatic field could be induced within the trap region. Essentially, this unrealistic level of control over the boundary potential could recreate the electrostatic fields induced by three-dimensional electrode sets (e.g., quadrupole conductors). Because planar electrostatic trap designs are limited to a discrete set of electrodes with fixed potentials, this level of ultimate control cannot be realized.

[0114] A well-known and interesting property of electrostatic fields (i.e., harmonic functions) is that every point within the region is an average of the field behavior along the boundary. Formally, the field at any point within the planar electrostatic trap can be expressed as a convolution over the boundary potential. This convolution process acts like a blurring process, so the potential in the midplane of an electrostatic trap is a blurring of the boundary potential.

[0115] For example, consider a square wave variation in the boundary potential of a two-dimensional planar electrostatic trap with a wavelength, λ, and a duty cycle, 0 < α < 1. The peak-to-peak variation of the n-th harmonic decays as follows Pn(y)=22nπ(1−cos(2πnα))12e−2πnΔy / λ, where n ≥ 1 and Δy is the displacement from the electrode boundary. This shows that higher spatial frequencies of the boundary potential decay exponentially with increasing displacement from the boundary. It should be noted that the contribution of each spatial frequency of the boundary decays by approximately 1 / 1000 at three wavelengths in the range. Referring now to Fig. Figure 10 shows the electrostatic potential along the boundary, which in one example is generated by a sinusoidally varying electrode interface, for four different distances from the boundary. The electrostatic potential is generated by a sinusoidally varying electrode interface with a wavelength λ = 12 µm and a transition length L interface = 120 µm for increasing distance from the boundary. The trap height is assumed to be 60 µm.

[0116] Fig. Figure 10 thus illustrates this blurring effect and shows the electrostatic potential for increasing distance from the boundary electrode. It shows that strong variations in the boundary potential almost completely disappear after a shift of the order of a single wavelength.

[0117] Next, referring to Fig. 11 are variations of the electrostatic potential caused by the Fig. 10 shown sinusoidal electrode interface is generated, with increasing distance from the electrode. Fig. Figure 11(a) shows the standard deviation of the potential in the transverse x-direction along the longitudinal z-axis of the trap. The “ideal” of zero deviation is also shown (thick solid black). Fig. Figure 11(b) presents the same data on a log-linear scale. It can be seen that the standard deviation quickly approaches the limit of numerical simulations ~10-5 with increasing distance from the electrode. This standard deviation of the electrostatic field, i.e., the deviation from an "ideal" (constant) potential, is therefore plotted as a function of distance from the electrode. By exploiting this uncertainty property of electrostatic fields, it is possible to approach the limit of highest control over the limiting potential described above using only a discrete set of electrodes.

[0118] It will now Fig. 12, in which various curved electrode interfaces are shown, in particular: (a) a sinusoidal variation of an interelectrode boundary; (b) a square wave interface with boundary centerline curvature; and (c) an elongated strip electrode design with modulated duty cycle along the longitudinal axis of the trap. Fig. 12(a) and Fig. 12(b) thus demonstrate an additional level of control over the electrostatic field provided by corrugated electrode interfaces. This is advantageous in the design of electrostatic traps that exhibit minimal variation in ion time-of-flight with respect to energy, insertion angle, and position.

[0119] Next, referring to Fig. For comparison, Figure 13 shows an electrostatic field generated by straight and sinusoidally varying electrode interfaces along the boundary for four different (increasing) interface lengths, L interface , is induced. The trap height is assumed to be 60 µm. This demonstrates improved control and shows that the electrostatic potential gradient can be tailored using the length of the electrode interface.

[0120] Then Fig. 14A, in which an out-of-plane electric field, E y, along the centerline of a planar electrostatic trap (x = y = 0) for an axially offset trap (Δd axial = 1.0 µm) with sinusoidally varying electrode interfaces for four different (increasing) interface lengths, L interface , is shown. The trap height is assumed to be 60 µm. It is also Fig. 14B, in which, for comparison with Fig. 14A shows an out-of-plane electric field along the centerline of a planar electrostatic trap for an axially offset trap with rectangular wave varying electrode interfaces for four different interface lengths. Therefore, in Fig. 14A and Fig. 14B otherwise uses the same parameters.

[0121] Now referring to Fig. Figure 15 shows a boundary potential due to a square-wave electrode interface. Another advantage of corrugated electrode interfaces is the reduction of the strength of the out-of-plane electric fields (which is the y-axis 9 in Figure 15) induced by misalignment of the electrode plates along the longitudinal direction of the trap. This is shown in Fig. 14A, Fig. 14B and Fig. 15 shown.

[0122] The concept of corrugated electrode interfaces can be extended to collinear electrode strips maintained at different potentials. This is demonstrated, for example, in Fig. 12(c) specifically demonstrates this. By varying the duty cycle of the stripes along the transverse direction of the trap, the effect of varying intermediate potentials along the boundary can be achieved.

[0123] Next, referring to Fig. Figure 16 shows an electrostatic potential resulting from a strip electrode design for four different displacements from the electrode boundary, Δy boundary The wavelength of the stripe design is λ = 15 µm, and the duty cycle is periodically varied between 0.1 ≤ α ≤ 0.9. The trap height is assumed to be 60 µm. This drawing shows the boundary potential due to a set of stripe electrodes and the electrostatic potential with increasing displacement from the boundary, illustrating that the features of individual stripes are exponentially suppressed with increasing displacement into the trap.

[0124] It will now Fig. 17A, which shows the electrostatic potential of a stripe electrode design at (a) the boundary and (b) the centerline for an example with a linearly increasing duty cycle. Specifically, the duty cycle is increased from α = 0.1 → 0.85 over 180 µm. The wavelength of the stripe design in (b) is λ = 15 µm. The potential is induced in the center plane of the trap. The trap height is 60 µm.

[0125] It is also Fig. 17B, ​​which shows an electrostatic potential of a stripe electrode design at (a) the boundary and (b) the centerline for an example with a linearly increasing duty cycle, where a circular arc is implemented in the induced mid-plane potential by adjusting the shifting of the duty cycle variation of each stripe. Specifically, the duty cycle is increased from α = 0.1 → 0.85 over 180 µm. The wavelength of the stripe design in (b) is λ = 15 µm. The potential is induced in the mid-plane of the trap. The trap height is 60 µm.

[0126] Also referring to Fig. 18 is an electrostatic potential along the centerline of the trap due to the strip electrode design of Fig. 12(c). Fig. 17A, Fig. 17B and Fig. 18 show that using this principle, electrostatic lenses of any shape and with any potential gradient can be manufactured.

[0127] Next, referring to Fig. 19 are shown for an electrostatic trap design based on electrodes held at only two different potentials: (a) boundary potentials of the electrodes for positive voltage electrodes, grounded electrodes, and negative voltage electrodes; (b) a potential induced in the midplane of the trap; (c) a potential along the centerline of the trap. This corresponds to the potential in Fig. 9(c) shown design.

[0128] This strip electrode design principle can greatly reduce the number of different electrode potentials required for the fabrication and operation of high-performance electrostatic ion traps. Fig. 9(c) and Fig. 19 illustrate a design of an electrostatic trap that requires only two ungrounded electrode potentials. This design can reduce the electrostatic field generated by the straight electrode arrangement in Fig. 9(b), which uses electrodes held at six different, ungrounded potentials. Reducing the required number of different potentials can be a significant advantage in the construction of high-performance microscale electrostatic ion traps, given the stringent constraints on the fabrication and operation of these devices.

[0129] The Fig. 9(c) and Fig. The design shown in Figure 19 is merely an example of the strip electrode technique and should not be understood as the only possible formulation. Furthermore, the strip electrode approach can easily be extended to a design that uses only a single ungrounded electrode potential. Another advantage of strip electrodes can be improved control over the electrostatic potential within the trap. Consequently, they could enable the design of electrostatic traps with smaller time-of-flight variations for ions with different energies, different insertion angles, and different positions. As an example of this design process, it is assumed that a certain potential along the centerline of the trap ( Fig. 9, x = 0, y = 0), denoted by ψ(z), is desired. Since the electrostatic field inside the trap is determined by the boundary potential, the desired potential can be expressed as a convolution, ψ(z)=ϕ(0,0,z)=∫dx′∫dz′K(x−x′,y−y′,z−z′)f(x′,z′)|x=0,y=0, where K(x,y,z) is the null space and f(x,z) is the still undetermined limiting potential. Along the transverse x-axis, each strip electrode can be determined by the duty cycle at that longitudinal position, α(z). This can allow the limiting potential to be expressed in terms of the unknown duty cycle as f(x,z)=S(x / λ;α(z)), where S(x;α) is a square wave of unit period and duty cycle α. Substituting this equation into the previous equation, a non-linear Fredholm integral problem of the first kind for the unknown duty cycle can be set up as ψ(z)=T[α](z)=∫dz′T(z−z′,α(z′)), where the non-linear null space is given by T(z,α)=∫dx′K(x′,y,z)S(x′ / λ,α)|y=0.

[0130] Fast Fourier transform techniques can enable rapid evaluation of the convolution forms given in these last two expressions. This could allow the development of a solution for the duty cycle by discretizing and using standard regularization methods for Fredholm integral problems of the first kind. One example is the regularized nonlinear least squares formulation, α^=argminα∈B‖ψ(z)−T[α](z)‖2+μ‖α"(z)‖2, where the minimization is performed over a finite-dimensional basis set B and µ is the regularization parameter.

[0131] Returning to the general spirit of the disclosure discussed above, further details may be considered. For example, a boundary between at least some of the adjacent electrodes may have a wavy, modulated, or multiply curved shape. In some embodiments, at least some of the electrodes are strip electrodes. Then, a duty cycle of the strip electrodes may vary along the longitudinal axis of the ion trap. Optionally, the strip electrodes may be configured to define a lens. In this case, the strip electrodes may be configured to be maintained at different electrostatic potentials. In embodiments, the electrostatic potential received by the at least some of the electrodes of the first and second sets for confining ions may be a single, non-zero electrostatic potential.Alternatively, the electrostatic potential received by the at least some of the electrodes of the first and second sets for confining ions may be a discrete number of different non-zero electrostatic potentials, typically 2 or 3 different non-zero electrostatic potentials.

[0132] An alternative implementation of a µEST (which may be combined with any other implementation disclosed herein) is now considered. As stated above, a µEST is advantageously fabricated using microlithography and / or nanolithography technologies to achieve nanometer-scale tolerances on planar wafers. The detection electrodes advantageously have a low capacitance (below 1 pF) to enable single-charge detection. Each set of electrodes is formed on a planar substrate, and two substrates face each other to form the trap or a linear array of traps.

[0133] As previously stated, the structures are separated on each side (in a z-direction) by a spacer, which can typically have a dimension of 60 µm. The structures are aligned in the planar direction (perpendicular to the separation direction, i.e., in the x-direction and y-direction) with an accuracy better than 0.5 µm and a system-level parallelism better than 0.5 µm. Achieving this accuracy is difficult. High-precision positioning tools can be used, but these tools typically require specialized expertise, and the time-consuming alignment process is performed at the chip level. The approach described below uses a self-alignment method using high-precision anisotropic silicon etching in combination with a dielectric substrate.

[0134] Silicon can be etched with high precision using potassium hydroxide (KOH) or tetramethylammonium hydroxide (TMAH) solutions. These anisotropic processes exploit the monocrystalline nature of silicon. The (111) plane in this single crystal is a natural etch stop in this process. In standard (100) silicon wafers, the (111) plane is oriented less than 54.735° from the surface. When a rectangular shape is unmasked and etched with such solutions, an inverted pyramid, or V-groove, is created. The angles of these V-grooves have atomic precision. However, the position of the groove is limited by the lithography steps. The fundamentals of these etching processes are described in "KOH anisotropic silicon etching for MEMS accelerometer fabrication," Petteri Kilpinen, PhD thesis, Department of Materials Science and Engineering, Aalto University (2012).

[0135] This inverted pyramid appears to be a perfect slope for a precision ball. Such balls are available in many materials, such as sapphire, aluminum oxide, or stainless steel, with diameters greater than 0.2 mm and a variation from the perfect shape of less than 0.08 µm, as well as batch diameter variations of less than 0.13 µm (see "Precision Balls - with Maximum Rating," data sheet, Sapphire Movement).

[0136] Next, referring to Fig. Figure 20 schematically shows an approach for aligning two substrates of a µEST based on a ball positioned in grooves (in particular, V-grooves). A first groove or slope 401 is provided in a first substrate, and an opposing second groove or slope 402 is provided in a second substrate. A precision ball 403 positioned between the first slope 401 and the second slope 402 forms a precise alignment system. Upon application of force orthogonal to the substrate plane, both wafers are precisely aligned in all dimensions. This approach is similar to that disclosed in US Pat. No. 5,639,387, but is used for alignment in optical applications.

[0137] Various techniques are available to permanently fix the substrates in this position. Suitable bonding techniques may include, for example, adhesive bonding, soldering, or thermocompression bonding. The accuracy is limited by the accuracy of the balls, the etch depth, and the lithography. The distance g between the substrates can be calculated using the following equation. g=2(rsin(90°−α)−d), where g is the distance between the substrates, d is the depth of the groove, r is the radius of the sphere (in Fig. 20 not shown) and α stands for the orientation angle of the (111) plane.

[0138] With suitable spheres, such as sapphire spheres with a radius of 150 µm + / - 0.125 µm, and precise groove etching of, for example, 229.8 µm + / - 0.5 µm depth, a pitch precision of 60 µm + / - 1.5 µm is achievable. When using V-grooves, the etch rate is reduced by a factor of 400 when the (111) planes coincide. Depth precision in this case is primarily defined by the lithography rather than the etch rate. Parallelism is likely to be even better, as etch depth and lithography are much better at the chip level than at the wafer level.

[0139] Lateral precision may depend on the precision of the lithography. This can allow for lateral precision better than 0.5 µm when using a stepper.

[0140] In this approach, alignment is performed at the chip level, but it is also possible to perform alignment at the wafer level. To define the lateral position and establish a stable pitch when performing alignment at the chip level, at least three balls per chip can be used. At the wafer level, either three balls per chip or at least three balls per wafer can be used.

[0141] These fixtures can be applied after alignment to fix the alignment position of wafers. These connections can also be used to form electrical connections between wafers.

[0142] Variations of this general alignment approach are also possible. Anisotropic dry etching techniques can be used to form precise slopes. Fibers can also be used instead of spheres, with similar results. Any object where the precision dimension of the spacing matches that of the groove may be suitable. For the reasons stated above, silicon is preferred, but alternatives can also be considered using suitable substrate materials that allow etching resulting in grooves of suitable precision.

[0143] Although this approach relies on the use of silicon as a substrate, it can lead to other problems. A silicon substrate can lead to high parasitic capacitances in the detection pads, which can complicate single-ion detection. However, anisotropic etching techniques may not be possible with other materials. Another approach involves depositing the surface metallization on silicon over an interlayer dielectric, such as SiO2 or SiN4, with a thickness of up to several µm. In other words, a dielectric layer is inserted between a silicon substrate and a surface metallization. During silicon etching, the dielectric layer can remain in place. This can reduce parasitic capacitances while enabling alignment by silicon etching, as described above.Therefore, this approach can be combined with the silicon etching-based alignment technique.

[0144] Now referring to Fig. Figure 21 illustrates a schematic structure for an alternative alignment approach, in which surface metallization is deposited on an interlayer dielectric layer. This effectively shows a cross-section in the xy plane, showing a silicon substrate 410 from which a portion 415 (beneath critical features) has been removed from the backside using anisotropic etching. The metal features are aligned from the top silicon substrate to the bottom silicon 440. To meet the desire for low capacitance of the detection areas, the substrate is etched down to the oxide layer 430. Electrical contacts 420 are provided for interconnection purposes.

[0145] This approach enables precise alignment along with the desired electrical properties based on a combination of techniques to form an improved electrostatic trap with single-ion sensitivity.

[0146] Although embodiments according to the disclosure have been described with reference to certain types of devices and applications (particularly mass spectrometry), and the embodiments have particular advantages in such a case, as discussed herein, approaches according to the disclosure may be applied to other types of devices and / or applications. In particular, the devices according to the disclosure may be used for other applications. The specific structure, arrangement, and operational details (e.g., potentials) of the μEST and / or the array of μESTs and associated uses, while potentially advantageous (particularly with regard to known configurations and capabilities), may be varied considerably to achieve operating modes with similar or equal performance. The scale of the μEST may also vary widely, for example, from the nanometer to the millimeter range.Certain features may be omitted or substituted, for example, as indicated herein. Any feature disclosed in this specification may, unless otherwise indicated, be replaced by alternative features serving the same, equivalent, or similar purpose. Thus, unless otherwise indicated, each disclosed feature represents only one example of a generic set of equivalent or similar features.

[0147] In this detailed description of the various embodiments, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. However, one skilled in the art will recognize that these various embodiments may be practiced with or without these specific details. Moreover, one skilled in the art can readily appreciate that the specific sequences in which methods are presented and performed are illustrative, and it is contemplated that the sequences may be varied and still remain within the scope of the various embodiments disclosed herein.

[0148] Although Fig. While Figure 1A shows a basic design for a µEST, some modifications are possible. For example, it may not be necessary to have two detection electrodes on each substrate. An alternative approach could provide the detection electrodes on only one substrate. The detected signal may be halved as a result, but the capacitance is also reduced (which may affect noise pickup), so the signal-to-noise ratio may only be reduced by √2. Another alternative could be to use a single detection electrode. This is less preferred because two electrodes are better suited for differential detection and common-mode rejection.

[0149] The number and positioning of the accelerating and / or reflecting electrodes can be varied. It is expected that at least one accelerating electrode and at least one reflecting electrode will be used on each side (in the Z dimension) of each electrode set (i.e., four accelerating electrodes and four reflecting electrodes). In some configurations, it may be possible to use fewer accelerating electrodes. A different µEST design may also allow for a reduction in the number of reflecting electrodes.

[0150] A wide variety of manufacturing technologies can be used, including: glass on silicon, cryogenic silicon, wafer polishing, precise alignment techniques, and the like.

[0151] There may also be a variation of the Fig. 2 shown µEST can be considered. For example, the number of electrodes and / or the applied potentials can be changed significantly. The curvature of the electrodes in the design of Fig. 2 only concerns the electrodes in the z<0 part (left side), but in some implementations, the other electrodes (on the z>0 side or the right side) could also be curved. The number of possible variations of this basic design is essentially infinite.

[0152] As used herein, including the claims, singular forms of terms should be construed to include the plural form and vice versa, unless the context indicates otherwise. For example, unless the context indicates otherwise, throughout this document, including the claims, a singular reference such as "a" or "an" (such as an ion multipole device) means "one or more" (such as one or more ion multipole devices). Throughout the description and claims of the present disclosure, the words "comprise," "include," "have," and "contain," and variations of these words, such as "comprising" and "comprises," or the like, mean "including, but not limited to," and are not intended to exclude (and do not exclude) further components.Furthermore, the use of “or” is inclusive, such that the expression “A or B” is true if “A” is true, “B” is true, or both “A” and “B” are true.

[0153] The use of any and all examples or exemplary language provided herein ("for example," "such as," "such as about," and the like) is intended only to better illustrate the disclosure and does not imply any limitation on the scope of the disclosure unless otherwise claimed. Language in the description should not be construed as indicating that any unclaimed element is essential to practicing the disclosure.

[0154] The terms "first" and "second" may be interchanged without changing the scope of the disclosure. That is, an element referred to as a "first" element may instead be referred to as a "second" element, and an element referred to as a "second" element may instead be considered a "first" element.

[0155] All steps described in this specification may be performed in any order or simultaneously, unless otherwise stated or unless the context requires otherwise. Furthermore, the description of a step as being performed after another step does not preclude the performance of intervening steps.

[0156] It is also understood that for any given component or embodiment described herein, any of the possible candidates or alternatives listed for those components may generally be used individually or in combination with one another, unless otherwise implicitly or explicitly understood or stated. It is understood that any list of such candidates or alternatives is illustrative only and not limiting, unless otherwise implicitly or explicitly understood or stated.

[0157] All literature and similar materials cited in this disclosure, including, but not limited to, patents, patent applications, articles, books, contracts, and Internet websites, are expressly incorporated by reference in their entirety for all purposes. Unless otherwise described, all technical and scientific terms used herein have a meaning as commonly understood by one of ordinary skill in the art to which the various embodiments described herein belong. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Zitierte Patentliteratur

[0000] US 17 / 823,618

[0002] WO 2013110587

[0003] WO 2019202338

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[0136] Cited non-patent literature

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[0003] AR Todd et al., J. Am. Soc. Mass Spectrom. 2020, 31, 146-154

[0004] Tolmachev et. al., Anal. Chem. 86 18 9162-9168 (2014

[0034] DZ Keifer, EE Pierson, MF Jarrold, Analyst 142, 1654 (2017

[0039] JS Brodbelt, et al., Chem. Rev. 120, 3328 (2020

[0069] P. Roepstorff, J. Fohlman, Biomed. Mass Spectrom. 11(11), 601(1984

[0081] KOH anisotropic silicon etching for MEMS accelerometer fabrication“, Petteri Kilpinen, PhD thesis, Department of Materials Science and Engineering, Aalto University (2012

[0134]

Claims

[1] Electrostatic ion trap comprising: a first set of planar electrodes distributed along a longitudinal axis of the ion trap; a second set of planar electrodes distributed along the longitudinal axis of the ion trap, each of the electrodes of the second set being arranged to be spaced from and opposite a corresponding electrode of the first set; wherein at least some of the electrodes of the first and second sets are configured to receive an electrostatic potential to confine ions received in the space between the first and second sets of planar electrodes; and wherein a length of the first and second set of planar electrodes along the longitudinal axis is not more than 10 mm and / or wherein a capacitance of at least one of the electrodes to ground is not more than 1 pF. [2] The electrostatic ion trap of claim 1, wherein at least one of the electrodes is a detection electrode configured to detect an image current of trapped ions, and wherein the capacitance of the detection electrode to ground is not more than 1 pF. [3] An electrostatic ion trap according to claim 2, wherein: some of the electrodes are reflective electrodes configured to receive a reflective potential and located at the ends of the ion trap along the longitudinal axis; and some of the electrodes are acceleration electrodes configured to receive an acceleration potential and are located between the reflective electrodes and the detection electrodes along the longitudinal axis. [4] The electrostatic ion trap of claim 3, wherein the potentials at the reflective electrodes are selectively configured to be: at a lower level to allow ions to enter the ion trap; and at a higher level to confine the ions in the ion trap. [5] An electrostatic ion trap according to any one of claims 2 to 4, further comprising a transistor connected to the detection electrode. [6] An electrostatic ion trap according to any preceding claim, wherein the first set of electrodes is formed on a first planar substrate and the second set of electrodes is formed on a second planar substrate opposite the first planar substrate. [7] An electrostatic ion trap according to any preceding claim, wherein a distance between adjacent electrodes is not more than 100 µm. [8] An electrostatic ion trap according to any preceding claim, wherein the first and second substrates form part of an integrated circuit or wherein the first and second sets of electrodes are fabricated by lithographic techniques. [9] An electrostatic ion trap according to any preceding claim, wherein the arrangement of the second set of electrodes is substantially symmetrical between opposite sides of a center of the electrostatic trap along the longitudinal axis, and wherein the arrangement of the second set of electrodes is substantially symmetrical between opposite sides of a center of the electrostatic trap along the longitudinal axis. [10] An electrostatic ion trap according to any preceding claim, wherein one or both edges of at least some of the electrodes have an arc shape or at least some of the electrodes have a curved shape, an arc shape, a circular shape or an elliptical shape. [11] An electrostatic ion trap according to any preceding claim, wherein a boundary between at least some of the adjacent electrodes has a wavy, modulated or multi-curved shape. [12] An electrostatic ion trap according to any preceding claim, wherein at least some of the electrodes are strip electrodes, a duty cycle of the strip electrodes varying along the longitudinal axis of the ion trap. [13] An electrostatic ion trap according to any preceding claim, wherein at least some of the electrodes are strip electrodes configured to define a lens, the strip electrodes being configured to be maintained at different electrostatic potentials. [14] An electrostatic ion trap according to any preceding claim, wherein the electrostatic potential received by at least some of the electrodes of the first and second sets for confining ions is a single non-zero electrostatic potential. [15] An electrostatic ion trap according to any preceding claim, further comprising one or more spacers between the first and second sets of electrodes. [16] The electrostatic ion trap of claim 15, wherein at least one of the one or more spacers is conductive to couple at least one electrode on the first electrode set to at least one electrode on the second electrode set. [17] An electrostatic ion trap according to any preceding claim, wherein the electrostatic ion trap is configured such that one or more of: a measurement time is not more than 20 ms; an acceleration voltage is not more than 200 V; and a gas pressure in the electrostatic ion trap is not more than 10 -7 mbar. [18] An electrostatic ion trap according to any preceding claim, configured to receive no more than 100 ions injected into the electrostatic ion trap. [19] An electrostatic ion trap according to any preceding claim when dependent on claim 3, configured to select ions by applying a pulsating voltage to one of the reflective electrodes, thereby causing at least some ions to leave the trap. [20] An electrostatic ion trap according to any preceding claim, further comprising: a UV or IR laser configured to emit a pulse at a capture region of the electrostatic ion trap to thereby fragment ions trapped in the capture region. [21] The electrostatic ion trap of claim 20, wherein the laser is configured to emit the pulses in a direction orthogonal to the longitudinal axis of the electrostatic ion trap. [22] An electrostatic ion trap according to claim 20 or claim 21, wherein the laser is configured to: emit a single laser pulse whose timing is synchronized with a trajectory of a target ion; or emit multiple laser pulses that are not synchronized with a trajectory of a target ion. [23] An electrostatic ion trap according to any one of claims 20 to 22, further comprising: a controller configured to control the laser to fragment ions in the capture region and to receive a signal from the detection electrodes to detect ions fragmented in the capture region. [24] The electrostatic ion trap of claim 23, wherein the controller is further configured to control the repetition of fragmentation and detection to thereby generate an MS n -operation in the electrostatic ion trap. [25] The electrostatic ion trap of claim 24, wherein the controller is configured to control fragmentation in response to information determined from a previous detection. [26] An array of electrostatic ion traps, each ion trap having a longitudinal length of not more than 10 mm and / or at least one electrode having a capacitance to ground of not more than 1 pF, the array comprising an inlet for receiving an ion beam configured to trap a portion of the ion beam in each of the ion traps. [27] An arrangement according to claim 26, wherein each electrostatic ion trap comprises: a first set of planar electrodes distributed along a longitudinal axis of the respective ion trap; a second set of planar electrodes distributed along the longitudinal axis of the respective ion trap, each of the electrodes of the second set being arranged to be spaced from and opposite a corresponding electrode of the first set; wherein at least some of the electrodes of the first and second sets are configured to receive an electrostatic potential to confine ions received in the space between the first and second sets of planar electrodes; and wherein a length of the first and second sets of planar electrodes along the longitudinal axis is not more than 10 mm and / or at least one of the electrodes of the first and second sets has a capacitance to ground of not more than 1 pF. [28] An arrangement according to claim 26 or claim 27, wherein the arrangement is configured with a plurality of electrostatic ion traps in the same plane and / or with a plurality of electrostatic ion traps in different planes. [29] Arrangement according to one of claims 26 to 28, further comprising: a UV or IR laser configured to generate a pulse; a splitter arrangement configured to spatially divide the generated pulse into parts and direct each part along a respective different plane; and a lens assembly comprising a plurality of lenses, each lens configured to focus a respective portion of the generated pulse into a respective collimated beam. [30] An arrangement according to any one of claims 26 to 29, configured to receive ions from a single ion beam in a plurality of electrostatic ion traps of the arrangement and to process the received ions in parallel in the plurality of electrostatic ion traps. [31] Arrangement according to one of claims 26 to 30, further comprising: a controller configured to control the transmission of an ion beam to at least one electrostatic ion trap of the array, the ion beam including at least one ion having a chromogenic tag or a tandem mass tag. [32] A method for analyzing an ion beam comprising a mixture of different analyte ions, the method comprising: directing ions from the ion beam to a plurality of electrostatic ion traps of an array of electrostatic ion traps, each electrostatic ion trap having a longitudinal length of not more than 10 mm and / or at least one electrode with a capacitance to ground of not more than 1 pF; Obtaining signals indicative of mass and charge data relating to the ions from the plurality of electrostatic ion traps; and Combining the mass and charge data obtained from the signals to identify components of the mixture. [33] The method of claim 32, further comprising: Fragmenting precursor ions in the plurality of electrostatic ion traps to obtain fragment ions; wherein the step of obtaining signals indicative of mass and charge data comprises obtaining signals by analyzing the precursor ions in the plurality of electrostatic ion traps and / or obtaining signals by analyzing the fragment ions in the plurality of electrostatic ion traps; and wherein the step of combining the mass and charge data comprises combining the mass and charge data relating to the precursor ions and / or mass and charge data relating to the fragment ions. [34] The method of claim 33, wherein the steps of fragmenting, obtaining signals, and combining the mass and charge data are repeated sequentially. [35] A method according to any one of claims 32 to 34, wherein the step of obtaining signals comprises simultaneously analyzing ions in each of the plurality of electrostatic ion traps.

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