Uniform flow control for a multipassage microfluidic sensor

Microfluidic sensors have been very effective for rapid, portable bioanalysis, such as in determining the pH of a sample. By simultaneously detecting multiple chemicals, the overall measurement performance can be greatly improved. One such method involves a series of parallel microchannels, each of which measures one individual agent. For unbiased readings, the flow rate in each channel should be approximately the same. In addition, the system needs a compact volume which reduces both the wasted channel space and the overall device cost. To achieve these conditions, a manifold was designed using a tapered power law, based on a concept derived for electronics cooling systems. This manifold features a single feed passage of varying diameter, eliminating the excess volume from multiple branch steps. The design was simulated using computational fluid dynamics (CFD), which demonstrated uniform flow performance within 2.5% standard deviation. The design was further examined with microparticle image velocimetry (PIV), and the experimental flow rates were also uniform with approximately 10% standard deviation. Hence, the tapered power law can provide a uniform flow distribution in a compact package, as is needed in both this microfluidic sensor and in electronics cooling applications.