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Electron microscope image showing an array of microfabricated polyurethane channels having dimensions similar to those of the human capillaries which connect arteries to veins. The channels have a width of 5 microns (millionths of a meter) and lengths ranging from 20 microns to 110 microns in 10-micron steps. In researchers experiments, researchers sent fluorescently labelled human blood cells from the top to the bottom.
Sending fluorescently labelled white blood cells through the channels, the researchers observed that T-lymphocytes (red) avoided sticking to regions on the channel walls already occupied by groups of granulocytes and monocytes (both labelled green). This unexpected self-sorting process suggests a sort of physical communication between the different types of cells. Flow direction in this image is from the right to the left.
This research is described by Robert H. Carlson, Christopher V. Gabel, Shirley S. Chan, Robert H. Austin, James P. Brody, and James Winkleman in the 15 September 1997 issue of the journal Physical Review Letters
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