Sequential Differential Mobility Analyzer for Particle Separation
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Solution Overview
Problem
Traditional differential mobility analyzers (DMAs) face limitations in resolution due to diffusion, turbulence, and particle distribution, and fail to effectively separate target ions or charged particles from non-target particles, leading to reduced detection efficiencies and particle dilution.
Innovation Solution
A sequential differential mobility analyzer with multiple non-overlapping analysis regions within the same housing, utilizing guide electrodes and controlled electrical fields to direct target particles into a second DMA region without the need for a pump, enhancing separation and transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional DMA with two electrodes is used, then the device complexity is low, but the resolution and separation efficiency are limited
Solution Approach 1:
The DMA is divided into multiple sequential analysis regions (first DMA analysis region, second DMA analysis region, etc.) within the same housing. Each region has its own electrode pairs creating independent electrical fields, allowing multi-stage separation of particles with different electrical mobilities to achieve higher resolution
Solution Approach 2:
Multiple DMA analysis regions are nested within a single housing structure. The electrode pairs are arranged concentrically or sequentially within the same physical enclosure, with each region containing smaller particles or specific size ranges, creating a nested configuration that improves resolution without proportionally increasing external device size
2Productivity
If sheath flow is directed inwardly toward central exit to improve particle transport efficiency, then transport efficiency improves, but resolving power decreases due to diffusive crossing of unwanted particles
Solution Approach 1:
The flow path is segmented into multiple sequential regions with controlled flow directions. Inward flow is used in some regions for transport efficiency, while outward or lateral flow is used in other regions to prevent diffusive crossing and maintain resolving power, achieving both high productivity and measurement precision
Solution Approach 2:
Different flow directions are applied in different spatial regions. The sheath flow direction is locally optimized for each DMA region based on the specific separation requirements of particles in that region, with inward flow where transport efficiency is prioritized and outward/lateral flow where resolving power is prioritized
3Productivity
If classified aerosol flow rate is increased to achieve sufficient transport efficiency, then transport efficiency improves, but target particles are diluted reducing detection efficiency
Solution Approach 1:
The particle classification and concentration process is segmented into multiple stages across sequential DMA regions. Each region selectively removes specific particle sizes, progressively concentrating the target particles while maintaining manageable flow rates, achieving both high transport efficiency and high target particle concentration for detection
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
Improves the resolution and detection efficiency of target particles by minimizing particle loss and dilution, allowing for highly concentrated target particles to be extracted for further analysis, such as in mass spectrometry, without the need for external pumping.
Implementation Method 1
The electrical mobility of a charged particle is inversely related to the particle's size; smaller particles exhibit greater mobility within an electrical field than do larger particles (of like charge). By calibrating and coordinating the parameters of both the airflow and the gradient(s) of the electrical field(s) transversing the airflow route(s), smaller-than-targeted particles can be electronically attracted while larger-than-targeted particles continue being swept downstream with the airflow
Implementation Method 2
larger particles travel more in a 'downwind' direction during its longer residence time in the drift region due to their smaller electrical mobilities
Implementation Method 3
A sheath gas inlet permits sheath gas (or sheath gas, collectively 'sheath gas') to flow into the instrument between the electrodes, which draws the polydispersed particles through the annular region
Data Source
AI summary
The invention is essentially a sequential (“DMA”) apparatus using a novel arrangement of at least three electrodes and at least two block electrodes to produce a DMA apparatus having at least two sequential DMA regions between pairs of adjacent electrode walls within the same housing. This apparatus is used to improve the transfer of particles into the subsequent DMA region without a vacuum or pump, and to improve the separation of target particles from non-target particles and concentration and collection of the target particles.