Potentiometric multichannel cytometer microchip for high-throughput microdispersion analysis

The parallelization of microfluidic cytometry is expected to lead to considerably enhanced throughput enabling point-of-care diagnosis. In this article, the development of a microfluidic potentiometric multichannel cytometer is presented. Parallelized microfluidic channels sharing a fluid path inevitably suffer from interchannel signal crosstalk that results from electrical coupling within the microfluidic channel network. By employing three planar electrodes within a single detection channel, we electrically decoupled each channel unit, thereby enabling parallel analysis by using a single cytometer microchip with multiple microfluidic channels. The triple-electrode configuration is validated by analyzing the size and concentration of polystyrene microbeads (diameters: 1.99, 2.58, 3, and 3.68 μm; concentration range: ∼2 × 10⁵ mL^-1 to ∼1 × 10 ⁷ mL^-1) and bacterial microdispersion samples (Bacillus subtilis, concentration range: ∼4 × 10⁵ CFU mL^-1 to ∼3 × 10⁶ CFU mL^-1). Crosstalk-free parallelized analysis is then demonstrated using a 16-channel potentiometric cytometer (maximum cross-correlation coefficients |r|: < 0.13 in all channel combinations). A detection throughput of ∼48 000 s^-1 was achieved; the throughout can be easily increased with the degree of parallelism of a single microchip without additional technical complexities. Therefore, this methodology should enable high-throughput and low-cost cytometry.