Aerosol Mobility Imaging for Rapid Particle Sizing
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Solution Overview
Problem
Current technologies for measuring particle size spectra in the ultrafine and sub-micrometer range are either slow or lack the sensitivity needed for precise, rapid measurements at typical atmospheric concentrations, failing to provide both time resolution and sizing precision required for atmospheric measurements.
Innovation Solution
The Aerosol Mobility Imaging (AMI) system uses a parallel plate dimensional electrical mobility separator combined with laminar flow water condensation to rapidly size particles, where particles are separated by mobility, enlarged through water condensation, and imaged onto a CCD array for instantaneous recording of particle number concentration, enabling rapid measurement of ultrafine particle size distributions with seconds-order time resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If differential mobility sizing is used to measure particle size spectra, then sizing precision is improved, but measurement time increases to several minutes
Solution Approach 1:
The patent divides the particle size measurement range into multiple segments by using multiple electrometers positioned at different locations along the drift tube. Each electrometer measures a specific mobility size range simultaneously, allowing the complete size distribution to be captured in parallel rather than sequentially scanning through each size class one at a time.
Solution Approach 2:
The patent transitions from a single-point measurement approach to a multi-point spatial distribution approach by placing multiple electrometers along the drift tube collection electrode. This spatial dimensionality enables simultaneous measurement of multiple mobility sizes at different positions along the tube, converting a time-consuming sequential process into a parallel measurement system.
2Loss of time
If electrometer-based mobility sizing is used to achieve fast measurements, then time resolution is improved, but detection sensitivity deteriorates due to electrometer noise and multiple charging
Solution Approach 1:
The patent introduces a condensation particle counter as an intermediary detection device that receives particles from the drift tube. This intermediary system uses condensation to enlarge particles to a size suitable for optical detection, thereby bridging the gap between the fast electrometer measurement capability and the sensitivity requirements for detecting low concentrations of ultrafine particles in the atmosphere.
Solution Approach 2:
The patent changes the detection parameter from direct electrical charge measurement (which suffers from noise and multiple charging) to optical detection of condensed particles. By transforming particles through condensation to a different physical state and size, the system achieves both fast measurement capability and high detection sensitivity for low concentration atmospheric particles.
3Productivity
If scanning mobility particle spectrometer is used to rapidly scan drift tube voltages, then measurement speed is improved, but complete size distribution characterization still takes more than one minute
Solution Approach 1:
The patent performs preliminary action by pre-positioning multiple electrometers along the drift tube collection electrode before measurement begins. This preliminary arrangement allows the system to immediately measure multiple mobility sizes simultaneously when particles enter the drift tube, eliminating the need for sequential voltage scanning and reducing the time to characterize complete size distribution to seconds rather than minutes.
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 AMI system achieves rapid, precise measurements of particle size distributions with high sensitivity, comparable to scanning mobility particle spectrometers, while maintaining laminar flow and efficient particle activation, capable of detecting particles as small as 10 nm and covering a wide size range in a single image.
Implementation Method 1
Particles are separated spatially within the electrical mobility separator, enlarged through water condensation, and imaged onto a CCD array. The mobility separation distributes particles in accordance with their size.
Implementation Method 2
enlarged through water condensation, and imaged onto a CCD array. The mobility separation distributes particles in accordance with their size. The condensation enlarges size-separated particles by water condensation while they are still within the gap of the mobility drift tube.
Implementation Method 3
Once enlarged the particles are illuminated by a laser. At a pre-selected frequency, typically 10 Hz, the position of all of the individual particles illuminated by the laser are captured by CCD camera.
Data Source
AI summary
A parallel plate dimensional electrical mobility separator and laminar flow water condensation provide rapid, mobility-based particle sizing at concentrations typical of the remote atmosphere. Particles are separated spatially within the electrical mobility separator, enlarged through water condensation, and imaged onto a CCD array. The mobility separation distributes particles in accordance with their size. The condensation enlarges size-separated particles by water condensation while they are still within the gap of the mobility drift tube. Once enlarged the particles are illuminated by a laser. At a pre-selected frequency, typically 10 Hz, the position of all of the individual particles illuminated by the laser are captured by CCD camera. This instantly records the particle number concentration at each position. Because the position is directly related to the particle size (or mobility), the particle size spectra is derived from the images recorded by the CCD.