This award will support collaborative research in biophysics between Dr. Robert Gould, Middlebury College and Dr. W. Terence Coakley, University of Wales, Cardiff. The objective of the project is to exploit the use of ultrasound to segregate and isolate large particles of biological interest. When an ultrasonic standing wave field exists in a liquid-filled chamber, suspended particles of a given type will tend to collect at positions in the chamber about a half wavelength apart. The ultrasonic phenomena of radiation pressure and acoustic streaming associated with a standing wave field produce forces and torques on objects in suspension. Strengths of the forces and torques on a given particle depend mainly on the size and shape of the particle and on the acoustical properties of compressibility and density of the particle, relative to the corresponding properties of the suspending liquid. Thus particles differing in acoustic properties will tend to collect in different positions in the chamber. Methods for collecting particles in suspension with which most biologists are familiar, such as centrifugation, dielectrophoresis and application of magnetic fields, tend to cause particles to migrate to one or two sites. Ultrasound offers a unique capability to concentrate particles at many discrete locations in the suspending phase. This project aims to utilize the differences in the forces and torques on different types of particles to diverge them, one type from another, so they may be harvested and studied separately. The results of this research will provide important information regarding the applicability of ultrasound to a variety of biological systems. The project will benefit from the complementary expertise of the two investigators, as well as their past history of fruitful collaboration.
