Authors: S. Africk and C.K. Colton
Affilation: Prodyne Corp. and Massachusetts Institute of Technology, United States
Pages: 827 - 829
Keywords: nanotechnology, ultrasound, nanoparticles, backscatter, quality control
Originally developed to measure concentration of human Islets of Langerhans in transplant preparations, the Ultrasonic Pulsed Doppler (USPD) method uses a single transducer as both source and receiver of pulsed ultrasound to measure backscattered energy from suspended and moving particles. Particle motion can be provided mechanically (e.g. by stirring or unidirectional flow) or by acoustic streaming generated by the interrogating acoustic field itself. The objective of this study has been to extend this methodology to submicron particles. Suspensions of emulsions (approximately150 nm diameter), polymer beads (40 nm), dendrimers (4 nm) and carbon nanotubes (10 nm diameter) were examined. Backscatter spectra were obtained for all types of particles with concentrations ranging from 0.04 to 10 % by weight. This suggests that the method can be used to measure concentration for a variety of submicron particles. Other potential applications are particle size distribution, suspension viscosity, sample purity, and particle compressibility. The system is proposed as a quality control device for bioprocessing or nanomanufacturing in batch mode or as an on-line monitor of a stream of particles.