Modified cell-flow microchannels in a single-crystal silicon substrate and flow behavior of blood cells

Previously reported cell-flow microchannels in a single-crystal silicon substrate (Microvasc. Res. 44, 226-240, 1992) have been modified, and flow behavior of blood cells is described using flow rate-time curves and video pictures. The principal structure (2600 identically sized channels in parallel) was retained to give the same simple quantitative measure of the total flow rate for blood cell suspensions under constant suction. Level areas (terraces) were placed at the entrance and exit sides of the parallel channels level with the channel depth (4.5 microns) so that blood cells just entering into and flowing out of the channels could be more clearly observed under reflecting illumination. Three lengths (10, 20, and 100 microns) of channel were used each with a terrace width of 30 microns. In agreement with calculated values, the resistance to flow at the terrace portion was shown to be nearly equal to that per 10 microns of the channel portion. Clearer pictures were obtained of channel blocking by activated leukocytes and platelet aggregates after addition of each stimulant. Erythrocyte aggregates showed easy transit even through the 100-microns-long channels and through narrow spaces, including gaps probably narrower than 2 microns, which were formed between plugging leukocytes at the terrace portion.