Partial Ovoidal FAIMS Electrode Alignment
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Solution Overview
Problem
The commercial development of spherical side-to-side High Field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS) is hindered by the difficulty in precisely aligning and constructing a practical spherical cell, which affects the ion focusing and transmission efficiency.
Innovation Solution
A partial ovoidal FAIMS design with inner and outer electrodes having adjacent surfaces shaped as portions of ovoids, truncated by a plane parallel or perpendicular to their axis, allows for precise and stable alignment using a base plate, enabling the application of asymmetric waveforms and compensation voltages for effective ion separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spherical electrodes are used in FAIMS device, then ion focusing capability is improved, but manufacturing precision and alignment difficulty increase
Solution Approach 1:
The spherical electrode design is segmented into multiple components: an inner spherical electrode, an outer spherical electrode, and a base plate. This segmentation allows each component to be manufactured and aligned separately, reducing the overall alignment complexity while maintaining the ion focusing capability of the spherical geometry.
Solution Approach 2:
The base plate serves as an intermediary component that facilitates precise alignment between the inner and outer spherical electrodes. By providing a stable mounting surface with precise geometric features, the base plate mediates the alignment process, making it easier to achieve the required precision without directly aligning the spherical electrodes to each other.
2Productivity
If spherical electrodes are used in FAIMS device, then ion transmission efficiency is improved, but device complexity increases
Solution Approach 1:
Dividing the device into modular components (inner electrode, outer electrode, base plate) simplifies the construction process while maintaining the ion transmission efficiency benefits of spherical geometry. Each module can be independently fabricated and assembled.
Solution Approach 2:
Instead of attempting to construct a complete spherical cavity and then align components within it, the design inverts the approach by using a base plate as the primary structural element and mounting the spherical electrodes to it. This reversal simplifies the construction sequence and reduces overall device complexity.
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 partial ovoidal design facilitates the construction of a robust and precise FAIMS device that maintains high ion transmission efficiency and resolving power, overcoming the alignment challenges of spherical designs while ensuring stable electrode alignment and efficient ion separation.
Implementation Method 1
The application of an asymmetric waveform to the inner electrode has an additional ion-focusing action that extends around the spherically shaped terminus of the inner electrode that causes the selected ions to be directed radially inwardly within the region proximate the inner electrode terminus.
Implementation Method 2
In IMS, gas-phase ions migrate in a drift tube in the presence of a constant electric field. Ions are separated by differences in their drift velocities. In FAIMS, ions are separated due to the dependent behavior of Kh as a function of the applied electric field strength.
Implementation Method 3
This transverse drift is compensated by applying a constant voltage to the first electrode, the 'compensation voltage' or CV. Hence, where multiple ions are present, only an ion whose drift is compensated can arrive at a detector for an appropriate combination of DV and CV.
Implementation Method 4
Ions to be separated are entrained in a stream of gas flowing through the FAIMS analyzer region. The net motion of an ion is the sum of an axial x-axis component due to the stream of gas and a transverse y-axis component due to the applied electric field.
Data Source
AI summary
A partial ovoidal FAIMS apparatus for separating ions is presented with inner and outer electrodes that have geometrically matched convex and concave partial ovoidal surfaces, respectively, that share at least one common defining axis and display a nearly constant displacement between the opposing surfaces. The ovoidal surfaces can be that of an egg shaped ovoid, an ellipse, or a sphere. The apparatus can have at least one ion inlet and an ion outlet where the outlet is on or as near as possible to a point on the defining axis in the outer electrode and the inlet or inlets are on, near, or symmetrically disposed about the defining axis of the ovoidal surfaces. Electrical contacts to the electrodes permit the application of an asymmetric waveform and a compensation voltage to at least one of the electrodes. The electrodes are positioned, stabilized, and insulated from each other by a base plate.