Scanning Opposed Migration Aerosol Classifier Voltage Dynamics
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Solution Overview
Problem
Existing scanning opposed migration aerosol classifiers face efficiency losses due to voltage scanning, which complicates instrument design and results in unacceptable particle losses and low transmission efficiencies, especially when measuring particles with varying mobilities over orders of magnitude.
Innovation Solution
A scanning opposed-migration ion and aerosol classifier that maintains the simplicity of constant voltage operation by understanding and simulating particle trajectories during continuous voltage variation, using numerical simulations of flow fields and electric fields to optimize particle transmission without adding spatial variations in voltages or cross-flow velocities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If voltage scanning is used to enable rapid measurement of particles with varying mobilities, then time response and productivity are improved, but particle transmission efficiency deteriorates due to unacceptable particle losses
Solution Approach 1:
The patent applies dynamics by making the electric field strength time-dependent through continuous voltage scanning. The electric field is dynamically adjusted to match the varying migration velocities of particles across different size ranges, enabling the instrument to adapt to particles with mobilities spanning orders of magnitude while maintaining high transmission efficiency throughout the scan.
Solution Approach 2:
The patent changes the electric field strength parameter continuously during particle measurement. By scanning the voltage applied to the electrodes, the system adjusts the electric field to optimize particle transmission at different mobility values, transforming a static parameter into a dynamic one that adapts to the measurement requirements.
2Reliability
If constant voltage operation is used to maintain high transmission efficiency, then particle transmission efficiency is preserved, but time response and measurement speed deteriorate
Solution Approach 1:
The patent implements continuity of useful action by maintaining continuous voltage scanning during the entire measurement process. Rather than switching between discrete voltage steps, the system continuously adjusts the electric field, ensuring that particles of all mobilities can be transmitted efficiently throughout the measurement cycle without interruption or loss.
3Adaptability or versatility
If scanning voltage is applied to measure particles across orders of magnitude in mobility, then adaptability and versatility are improved, but device complexity increases due to need for spatial variations in voltages or cross-flow velocities
Solution Approach 1:
The patent applies universality by using a single time-varying voltage applied uniformly across the electrodes to handle particles spanning orders of magnitude in mobility. This single scanning voltage mechanism serves multiple functions: it classifies particles across different size ranges, maintains transmission efficiency, and eliminates the need for complex spatial voltage variations or adjustable cross-flow velocities.
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 enables rapid classification of sub-nanometer particles with improved time response and duty-cycle, maintaining high transmission efficiency even during fast scans, allowing for measurement of nanometer particles with high time-resolution in applications like atmospheric nucleation experiments.
Implementation Method 1
Charged particles or ions (hereafter labeled particles) of appropriate polarity (positive or negative) are introduced at an upstream location through, or near one of the electrodes, and caused to migrate toward the counter-electrode by the electric field that is created when a voltage difference is applied between the two electrodes. The property on which this separation is based is the so-called electrical mobility, which is the steady-state migration velocity divided by the electric field strength
Implementation Method 2
A cross flow fluid enters the classification channel through one of the permeable walls and flows at a first velocity and exists in a first direction through the other permeable wall. An imposed field is applied that causes the particles to migrate in a direction opposite to that of the cross-flow fluid
Data Source
AI summary
An opposed migration classifier classifies particles suspended in a sample fluid that are passed through a classification channel defined by two permeable walls. Sample flow distribution input and output channels are located asymmetrically with respect to a center of the classification channel such that trajectories of the one or more particles in the sample fluid deviate from constant voltage operation trajectories. A cross-flow fluid enters the classification channel through a permeable wall and exits through the other permeable wall. An imposed field, created by a time varying filed imposed in a direction normal to the permeable walls, causes the particles to migrate in a direction opposite to that of the cross-flow fluid, such that the particles travel between the permeable walls. The particles in the sample are classified based on their mobility. The sample fluid enters and exists through or within a threshold distance of the permeable walls.