Authors: S.A. Africk, C.K. Colton
Affilation: Prodyne Corp., United States
Pages: 830 - 833
Keywords: nanoparticle characterization, ultrasonic backscatter, concentration, particle physical properties, particle size distribution, quality control, in-situ paricle monitoring
This paper describes a novel means for particle characterization, the Ultrasonic Pulsed Doppler (USPD) system. This system uses a single transducer to measure ultrasonic backscatter from moving particles to perform measurements of particle concentration, size (with better resolution than dynamic light scattering for small particles) and physical properties, including particle compressibility, which can be used to monitor particle functionalization. The essential phenomena of operation are (1) Rayleigh backscattering, the strength of which depends on the particle properties; (2) Doppler Effect, which shifts backscattered frequencies away from the interrogating frequencies; and (3) the interrogation of very small volumes, which facilitates the incorporation of the system into existing process hardware. The system can operate with high concentrations and opaque solutions. It can be used in batch mode or incorporated into processing equipment to provide in-situ and real time process monitoring and quality control. Examples of measurements that will be shown are: (1) frangibility of nanoparticle inks; (2) changes in backscatter of SDS micelles due to incorporation of acid molecules; and (3) changes in backscatter from BSA protein with changes in pH known to cause conformation changes.