Confocal imaging and numerical simulations of converging flows in artificial microvessels

A number of computational and experimental studies on flows in venular bifurcations have concentrated on the distribution of blood components and the formation of a ''separation surface'' between two converging flows with different red blood cell concentrations and viscosities. To better understand these phenomena, we have used microfabrication techniques to construct artificial venular bifurcations with physiologically realistic dimensions. The current apparatus consists of a single bifurcation formed from tubes with semicircular cross sections of radius 50 mu. The vessels are fabricated from two glass slides using an abrasive etching process and a low melting point glass as sealant. Using a laser scanning confocal microscope, we have obtained the first three-dimensional images of flow structures in microscopic vessels; in particular we have imaged the separation surface for converging Newtonian fluids. A quantitative comparison is made between finite element simulations and experimental results of the position of the separation surface for different inlet flow ratios. Computed positions of the separation surface at the mid-depth of the outlet branch are in excellent agreement with experimental results obtained by confocal microscopy.