Ion Modulator for Large Biomolecule DMS Analysis
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Solution Overview
Problem
Differential mobility spectrometers (DMS) struggle to effectively sort and differentiate larger molecules due to their small size and limited practical use, which restricts their application to small molecules, whereas traditional ion mobility spectrometers measure mobility directly, not differential mobility.
Innovation Solution
An ion modulating differential mobility spectrometer is introduced, featuring a channel with a differential mobility selector region and an ion modulator region that applies a longitudinal alternating current electric field, causing ions to bunch based on their mobility, allowing for the measurement of average mobility by comparing alternating current to direct current ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a traditional differential mobility spectrometer is used, then the instrument remains small and simple, but it cannot effectively sort and differentiate larger molecules
Solution Approach 1:
The patent nests an ion modulator region inside the existing DMS channel structure. The modulator applies a longitudinal AC field that causes ions to bunch before entering the differential mobility selector region. This nested approach extends the molecule size range without requiring a complete redesign of the compact DMS instrument.
Solution Approach 2:
The patent segments the ion analysis process into two distinct stages: (1) an ion modulator region that applies longitudinal AC field to bunch ions, and (2) a differential mobility selector region that performs the traditional transverse AC field separation. This segmentation allows each region to be optimized for its specific function while working together within a compact form factor.
2Adaptability or versatility
If traditional ion mobility spectrometry is used to measure mobility directly, then larger molecules can be detected, but the instrument becomes much larger and more complex
Solution Approach 1:
The patent merges the ion bunching function (traditionally separate) with the differential mobility selection function into a single integrated channel. The longitudinal AC field in the modulator region prepares ions for analysis, while the transverse AC field in the selector region performs separation, all within one continuous gas flow path, maintaining compactness while enabling larger molecule detection.
Solution Approach 2:
The ion modulator region performs preliminary action by applying a longitudinal AC field that causes ions to bunch before they enter the differential mobility selector region. This pre-bunching enhances the signal for larger molecules and improves their detectability without requiring a complete change to the instrument architecture.
3Productivity
If no ion bunching is applied, then the instrument operation is simple, but detection efficiency and signal-to-noise ratio are reduced
Solution Approach 1:
The patent implements periodic action through the longitudinal AC field applied in the ion modulator region. The field oscillates at a frequency that causes ions to bunch periodically as they traverse the modulator region, enhancing detection efficiency through coherent signal accumulation without requiring complex additional hardware.
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 approach enhances the ability to detect and separate larger molecules, improving the practical range of DMS spectrometry and enabling the identification of multiple species by observing functional orthogonality in nonlinear regimes, while reducing noise and increasing detection efficiency.
Implementation Method 1
ions in an electric field (E) experience a terminal velocity (v) that depends on their collision cross section, which is related to their mobility (K) in the following way: v=K*E
Implementation Method 2
The ion modulator region may include a longitudinal alternating current electric field along the axis of gas propagation
Data Source
AI summary
The tandem differential mobility spectrometer (DMS)-ion modulator instrument provides improved resolution relative to traditional DMS for molecules with larger masses. The instrument includes an ion-bunching electrode with an AC field synchronized to the transit time of the ion flow which is positioned downstream of a DMS. The ion bunching electrode produces a mobility-dependent modulation of the ion current. The ratio of AC to DC current provides a measure of the mobility of a large ion, even if it has little differential mobility, thereby extending the useful range of mobility characterization of a DMS system. The instrument is more compact than a larger traditional ion mobility spectrometer and does not require high voltages or high frequencies. Modulation before DMS separation or between tandem DMS separations produces a variable range of analyte and reactant ion densities as well as spatially separating negative and positive ions to reduce ion recombination.