Confocal imaging of flows in artificial venular bifurcations

We describe a new experimental methodology for visualising three-dimensional structures in microscopic tubes under flow conditions. Through the use of microfabrication techniques, artificial venular bifurcations are constructed front glass tubes with semicircular cross sections (radius = 50 mu). Aqueous fluorescent solutions are infused into the tubes at flow rates of about 1 mu l/min, a value comparable to blood flow in the microcirculation. The flow is imaged using a combination of confocal microscopy and three-dimensional image reconstruction software techniques. The quantitative accuracy of the experimental method is evaluated by measuring the "separation surface," a formation resulting from converging flows at a bifurcation. Derails of the fabrication process, fluidics, confocal microscopy, image reconstructions, optical effects, and computations are described We show the first three-dimensional visualization of a microscopic flow structure using confocal microscopy, and within certain limitations, quantitative agreement between the measured and computed positions of the separation surface.