AMI: Aerosol Mobility Imaging

What it does:

AMI is a instantaneous electrical mobility particle sizing system, providing high-resolution, 1-sec size distribution measurements for particles between 10 nm to 300 nm in diameter.


Objectives are to provide rapid measurements, such as for aircraft studies, and to speed measurement of particle hygroscopicity.

How it works:

AMI separates particles based on electrical mobility, then enlarges the particles along their flow trajectories, and photographs them. Images of particle positions within the gap , after mobility separation and condensational growth, are captured by a digital camera operating at 10 frames/sec. The images are analyzed to give the position, and hence mobility size, of each particle, from which the particle size spectrum at a time resolution of 1 Hz is derived.

The AMI System:

Particle images for mono-dispersed particles. By using a wide-range electrode, the electric field is varied spatially, with stronger field on the left side of this image. Theory predicts that particles of a uniform mobility will form an arc, which is exactly what is observed. Small particles are separated at low field (on the right) and larger particles are resolved in large field (on the left).  

25 nm particles

55 nm particles

100 nm particles