Researchers, Steven Africk and Clark K. Colton from Prodyne Corp. and MIT have developed an ultrasonic method for measuring nanoparticle concentration that may be extended to measuring size distribution, particle size and compressibility.
UltraSonic Pulsed Doppler (USPD) Technique
The technique used is an UltraSonic Pulsed Doppler (USPD) technique that measures ultrasonic power backscattered from suspended particles.
The method uses a single transducer and can be applied to particles in suspension and contained within almost any container. Acoustic energy in the form of unltrasonic energy is narrowly introduced into the container. The acoustic energy can cause movement in the suspension and subsequent Doppler effect measurements can be used to determine particle properties. may be introduced to a focal zone and narrow band interrogating signals may be used. The acoustic energy may cause movement or streaming of the fluid or suspension. The acoustic streaming may allow a Doppler effect measurement without any other source of velocity.
The USPD technique can be used to measure particle concentration, size (more precise than DLS) and mechanical compliance (for particle functionalization monitoring).
This process has been successfully applied to:
• Dendrimers (4 nm)
• TiO2 colloids (4 nm)
• Polymer beads (as small as 40 nm)
• Carbon nanotubes
• Perfluorocarbon emulsions
• Beta cells
• Murine embryonic stem cell aggregates (spheroids)
• Rat and human Islets of Langerhans