Flow Characteristics of Blood Cells and Yeast through Micromachined Channel Arrays

Abstract

Microgrooves (equivalent diameter 4-6μm; length 8-100μm (one size per chip); number 1300 or 2600 in parallel) formed in the surface of a single-crystal silicon substrate were converted to leak-proof microchannels by tightly covering them with an optically flat glass plate. Flow characteristics of blood cells and yeast through the microchannels were studied under constant suction.Erythrocytes suspended in autologous plasma, prepared from fresh heparinized blood obtained from healthy subjects, showed an extremely quick transit through the microchannels under suction of 20cmH2O; their mean transit time through 20μm long channels was estimated to be 0.7msec. Erythrocytes treated with 0.14% glutaraldehyde could not pass through the channels even under 200cmH2O suction.Leukocytes in whole blood took more than one hundred times longer than erythrocytes to pass through the microchannels. Their transit time was further increased by more than ten times when they were activated by 2nM of the chemotactic peptide FMLP (formy 1-methiony 1-leucy 1-phenylalanine).Yeast cells could not pass through the microchannels even under 200cmH2O but became passable under 20cm H2O when exposed to 60% ethanol. Protoplasts prepared from vegetative cells showed an easy transit through the microchannels.These results suggested the possibility of cell sorting by differences in cellular physiological state or activity using the microchannel arrays or other microchannel networks.