Real-time shape-based particle separation and detailed in situ particle shape characterization

Area of Science:

• Aerosol science
• Particle characterization
• Physical chemistry

Background:

• Particle shape significantly influences particle properties and behavior.
• Controlling and characterizing particle shape is challenging.
• Existing methods lack in situ, real-time shape analysis capabilities.

Purpose of the Study:

• To introduce a novel portable system for separating and characterizing particles by shape.
• To enable high-precision, in situ, real-time measurement of particle properties.
• To determine dynamic shape factors (DSFs) in different flow regimes.

Main Methods:

• Utilized an aerosol particle mass analyzer (APM) for mass-to-charge ratio classification.
• Employed a differential mobility analyzer (DMA) for charge and mobility diameter selection, isolating particles of uniform shape.
• Integrated the APM and DMA with a single-particle mass spectrometer (SPLAT II) to form the Aerosol Dynamic Spectrometer (ADS).

Main Results:

• The ADS system successfully separates particles based on shape.
• Demonstrated real-time measurement of individual particle composition, vacuum aerodynamic diameters, and DSFs.
• Characterized aspherical ammonium sulfate and NaCl particles, revealing a wide distribution of shapes with DSFs ranging from 1 to 1.5.

Conclusions:

• The developed portable ADS system provides unprecedented capabilities for shape-based particle separation and characterization.
• The system enables precise, in situ, real-time analysis of particle DSFs in transition and free-molecular regimes.
• The study highlights the significant variability in particle shapes for common aerosols like ammonium sulfate and NaCl.