FAIMS Ion Inlet Orifice Curvature for Gas Flow Guidance
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Solution Overview
Problem
Ion transmission in field-asymmetric ion mobility spectrometers is inefficient due to high velocity gas flows causing ion loss at the entrance, leading to poor ion transmission rates, typically around 10% as seen in the case of bromochloroacetate anion, with significant ion losses occurring on the inner electrode and entrance plate.
Innovation Solution
The implementation of a novel orifice structure that utilizes the Coand effect to guide the gas stream parallel to the inner walls of the outer electrode, combined with dual gas inlets to maintain pressure balance and symmetrical gas flows, and a modified electrode geometry with convex and concave surfaces to direct ions into the analytical gap with minimal deflection, reducing ion loss and enhancing transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high velocity gas flows are used to transport ions through the FAIMS cell, then ion transport speed is improved, but ion loss at the entrance and on the inner electrode increases significantly
Solution Approach 1:
The patent employs curved surfaces on the inner electrode and convex/concave geometries to redirect the gas flow and ions away from the problematic entrance region and inner electrode surfaces. The curved geometry guides ions through the analytical gap with minimal deflection, reducing ion loss while maintaining transport efficiency.
Solution Approach 2:
The patent introduces asymmetrical electrode configurations with convex and concave surfaces that create symmetrical gas flows. This asymmetrical design allows the gas to be redirected properly through the cell, preventing ion accumulation on the inner electrode while maintaining high transport speeds.
2Ease of manufacture
If conventional electrode geometry is used, then device simplicity is maintained, but ion transmission efficiency remains poor at around 10%
Solution Approach 1:
The patent modifies the electrode geometry by adding convex and concave surfaces that are relatively simple to manufacture. These curved surfaces efficiently redirect ions and gas flows, achieving over 10-fold improvement in ion transmission without requiring complex multi-component structures.
Solution Approach 2:
The patent applies localized geometric modifications to specific regions of the electrodes (convex surfaces on inner electrode, concave surfaces on outer electrode) rather than redesigning the entire device. This localized approach maintains overall device simplicity while dramatically improving ion transmission in the critical entrance and analytical gap regions.
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
This design significantly improves ion transmission efficiency by reducing ion losses at the entrance and within the analytical gap, achieving a 10-fold improvement in ion throughput with minimal redesign of the apparatus, ensuring more ions are directed into the mass spectrometer for analysis.
Implementation Method 1
The implementation of a novel orifice structure that utilizes the Coand effect to guide the gas stream parallel to the inner walls of the outer electrode
Implementation Method 2
a modified electrode geometry with convex and concave surfaces to direct ions into the analytical gap with minimal deflection
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A High Field Asymmetric Waveform Ion Mobility Spectrometry apparatus comprises (a) an expansion chamber receiving ions from an ion source and a gas flow from a gas inlet; (b) an outer electrode having a generally concave inner surface and comprising (i) an ion inlet orifice operable to receive ions from an ion source and a portion of the gas flow from the expansion chamber and (ii) an ion outlet; and (c) an inner electrode having a convex outer surface disposed in a spaced-apart and facing arrangement relative to the inner surface of the outer electrode for defining an ion separation region therebetween, wherein the portion of the gas flow and a portion of the ions are received into the ion separation region from the ion inlet, the apparatus being characterized in that a wall of the ion inlet orifice is convexly curved between an inlet end and an outlet end.