Overcoming the sensitivity vs. throughput tradeoff in Coulter counters: a novel side counter design*

Microfabricated Coulter counters are attractive for point of care (POC) applications since they are label free and compact. Mechanical clog formation - rendering the counter inoperable - increases markedly with reductions in the size of the constriction, leading to a tradeoff between sample throughput and sensitivity. We present a simple microfluidic coplanar Coulter counter device design that overcomes constriction clogging and is capable of operating in microfluidic channels filled entirely with highly conductive sample while being cost effective. The device employs microfabricated planar electrodes projecting into one side of the microfluidic channel and is easily integrated with upstream electronic, hydrodynamic, or other focusing units to produce efficient counting which could allow for dramatically increased volumetric and sample throughput.