Experimental setup for the ultrasonic fractionation of flowing whole blood in a capillary

Abstract

If a long ultrasound driving pulse is chosen such, that its frequency is greater than the resonance frequency of one cell type and less than the resonance frequency of another cell type, the cells are separated in different nodes and antinodes of the standing sound field. The purpose of this study was to build an experimental setup for the ultrasonic fractionation of whole blood in flow conditions. Blood fractionation is the separation of whole blood into its separate components, commonly used for analysis and transfusions. The experimental setup comprised a container with singleelement ultrasound transducers customisable in elevation and azimuth, focussed on a capillary through which blood was flowing. The acoustic focus coincided with the optical focus of a microscopic system to which a high-speed camera was attached. Ultrasound transducers were used with centre frequencies between 1MHz and 20MHz and with pressure amplitudes less than 1MPa. The duty cycle was greater than 10% in all experiments. The field of view was 0.2×0.2mm2. The optical resolution and camera speed allowed for visibility of red and white blood cells during flow conditions. Preliminary results show that red and white blood cells could be forced to move in opposite directions. The acoustic frequencies and pressures used were representative for those used in clinical diagnosis. We have shown that ultrasonic whole blood fractionation is feasible using ultrasound. Sonic fractionation speed might be an indicator for diseases such as malaria.

Keywords

• whole blood fractionation
• sonic cell separation
• radiation forces
• particle manipulation
• blood sonication