This study is concerned with separating particles suspended in a fluid by using field flow fractionation implemented with an ultrasonic acoustic force. In field flow fractionation (FFF), the fluid particle mixture is forced to flow through a thin channel. A force perpendicular to the direction of flow is applied. The action of the force on the particles is a function of the nature of the force, and the identity of the particles. To accomplish a particular separation of particles, one selects a force which acts with differing magnitude on the particles to be separated. As the particles move down the slit, the particles acted upon more strongly by the force move to the flow cell walls (if for example, the force acts towards the walls) where they slow down since the flow near the walls is slower. Those particles which were not caused to move towards the flow cell walls travel with a faster velocity and begin to distance themselves from the slower moving particles in the wall vicinity. Eventually, at the cell exit, the center moving particles elute first, and the slower moving particles exit later, thereby creating the separation. The utility of FFF for a particular separation depends on the ability to select a force which can drive the perpendicular separation. In this study, ultrasonic acoustic forces are used. Standing waves with a frequency on the order of 1 Mhz are set up across the flow cell, and the particles move by virtue of a second order acoustic pressure force as given by equation (1) of the proposal. The key advantage of using acoustic forces is that the acoustic force can separate particles based on differing volume, density or speed of sound in the particle medium. The research will design and conduct ultrasonic FFF flow cell, and investigate the ability to separate particles based on size and density.
