Microfabricated Quadrupole Lens for Mass Spectrometers
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Solution Overview
Problem
Miniature mass spectrometers face limitations in mass range, sensitivity, and noise levels due to RF heating and capacitative coupling issues in silicon-based electrostatic quadrupole mass filters, which restrict the voltage and frequency that can be applied, limiting mass range and resolution.
Innovation Solution
A microfabricated electrostatic quadrupole mass filter design that eliminates thin deposited oxide layers for electrical isolation, incorporates a grounded screen, and includes a Brubaker pre-filter by physically separating and attaching silicon parts to an insulating substrate, providing low capacitative coupling and improved sensitivity at increased mass resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thin deposited oxide layers are used for electrical isolation in silicon-based quadrupole mass filters, then device integration is simplified, but RF heating and capacitative coupling increase, limiting voltage and frequency application
Solution Approach 1:
The patent introduces an insulating substrate as an intermediary layer between silicon parts to provide electrical isolation. This mediator eliminates direct capacitative coupling between RF electrodes while maintaining device integration, thereby reducing RF heating effects and enabling higher voltage and frequency application without sacrificing manufacturing ease.
2Measurement precision
If higher voltage and frequency are applied to extend mass range, then mass range and resolution improve, but RF heating and capacitative coupling increase, limiting further voltage application
Solution Approach 1:
The insulating substrate acts as a mediator that reduces capacitative coupling between RF electrodes, thereby diminishing RF heating effects. This enables the system to operate at higher voltages and frequencies required for extended mass range and improved mass resolution without being constrained by thermal effects.
Solution Approach 2:
The patent segments the device into distinct silicon parts mounted on an insulating substrate, electrically isolating RF electrodes from each other. This segmentation reduces parasitic capacitative coupling and RF heating, allowing higher operating parameters for improved mass range and resolution.
3Device complexity
If silicon parts are integrated without physical separation, then device complexity is reduced, but capacitative coupling between electrodes increases, reducing sensitivity
Solution Approach 1:
The insulating substrate serves as a mediator that provides electrical isolation between silicon parts containing RF electrodes. This physical separation through an insulating intermediary reduces capacitative coupling between electrodes, thereby improving signal sensitivity and reducing noise without significantly increasing device complexity.
4Object-affected harmful factors
If grounded screen is added to reduce noise from stray ions, then noise level decreases, but device complexity and fabrication difficulty increase
Solution Approach 1:
The patent merges the grounded screen function with the insulating substrate structure. The insulating substrate is extended to form both the electrical isolation layer and the grounded screen that reduces noise from stray ions. This integration achieves noise reduction without proportionally increasing device complexity, as the screen is formed as part of the existing substrate structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances mass range, sensitivity, and reduces noise levels, allowing for higher voltage and frequency application, thereby improving the overall performance of miniature mass spectrometers.
Implementation Method 1
Ions are injected into the pupil between the electrodes, and travel parallel to the electrodes under the influence of a time-varying hyperbolic electrostatic field. This field contains both a direct current (DC) and an alternating current (AC) component.
Implementation Method 2
the provision of a miniature electrostatic quadrupole mass filter with high range, low noise and high sensitivity
Implementation Method 3
Noise arising from stray ions is conventionally reduced by the use of a grounded screen
Data Source
AI summary
This invention provides a method of aligning sets of cylindrical electrodes in the geometry of a miniature quadrupole electrostatic lens, which can act as a mass filter in a quadrupole mass spectrometer. The electrodes are mounted in pairs on microfabricated supports, which are formed from conducting parts on an insulating substrate. Complete segmentation of the conducting parts provides low capacitative coupling between co-planar cylindrical electrodes, and allows incorporation of a Brubaker prefilter to improve sensitivity at a given mass resolution. A complete quadrupole is constructed from two such supports, which are spaced apart by further conducting spacers. The spacers are continued around the electrodes to provide a conducting screen.