An ultrasonic scattering technique for microparticle characterization Free

A modified technique is presented for determining the physical properties of individual microparticles such as biological cells. Two submerged confocally positioned transducers (one transmitter/receiver and one receiver) generate 30‐MHz center frequency tone bursts which scatter off of single particles convected by a coaxial jet flow. The scattered pressure is measured at 90° and 180°, analog envelope detected, digitized, and stored in computer memory. By employing a long wavelength acoustic scattering theory first developed by Raleigh, it is possible to calculate the particle density and compressibility given a priori knowledge of both the particle volume and the physical properties of the host liquid. This apparatus, which is still in the developmental stage, is simpler and more versatile than an earlier, three‐transducer system developed by Mark Roos [Doctoral dissertation, Yale University (1983)]. The system performance and theoretical scattering model are evaluated using calibration particles (e.g., polystyrene spheres, liquid drops) and biological cells. [Work supported by NIH through grant number R01‐GM30419 and by ONR.]