Laminar flow dominates microscale applications in devices such as microvalves, pumps, and turbines and in biomedical applications such as stents and biological flows. Studies of pressure losses in junctions have mostly been focused on turbulent flow conditions that exist in larger scale piping systems. There is a need for laminar flow studies of energy losses in junctions and networks of junctions so that engineers can better predict, design, and analyze flow in microscale systems. Unlike in the turbulent regime, Reynolds number plays a dominant role in energy losses for laminar flow. Studies focused on Reynolds number dependence are needed.
This paper documents laminar flow experiments in networks constructed from microscale junctions (microjunctions). This work builds on previous experience of the authors in computational fluids dynamics simulations of junctions and networks of junctions. The planar junctions studied consist of circular tubes with two outlets and one inlet. A general technique has been developed to produce computer and physical models of junctions in which the inlet tube size is set, but the outlets are allowed to vary in size and angle relative to the inlet tube. A generalized algorithm has been implemented to create three-dimensional models of the junctions for both computational and experimental studies. There have been several techniques used to create the experimental microjunction networks: a “lost wax” method that creates the network in Polydimethylsiloxane (PDMS), stereolithography-based junctions connected by tubing, and photopolymer cured by ultraviolet radiation. Results are presented for pressure losses in various microjunction networks as a function of Reynolds number.