Electrokinetic flow and energy conversion in a curved microtube

Curved channels are ubiquitous in microfluidic systems. The pressure-driven electrokinetic flow and energy conversion in a curved microtube are investigated analytically by using a perturbation analysis method under the assumptions of the small curvature ratio and the Reynolds number. The results indicate that the curvature of the microtube leads to a skewed pattern in the distribution of the electrical double layer (EDL) potential. The EDL potential at the outer side of the bend is larger than that at the inner side of the bend. The curvature shows an inhibitory effect on the magnitude of the streaming potential field induced by the pressure-driven flow. Since the spanwise pressure gradient is dominant over the inertial force, the resulting axial velocity profile is skewed into the inner region of the curved channel. Furthermore, the flow rate in a curved microtube could be larger than that in a straight one with the same pressure gradient and shape of cross section. The asymptotic solutions of the axial velocity and flow rate in the absence of the electrokinetic effect are in agreement with the classical results for low Reynolds number flows. Remarkably, the curved geometry could be beneficial to improving the electrokinetic energy conversion (EKEC) efficiency.

Automated summary

In this study, the pressure-driven electrokinetic flow and energy conversion in a curved microtube in a microfluidic system were investigated. The results showed that the curvature of the microtube led to a skewed distribution of the electrical double layer potential. The curvature also had an inhibitory effect on the magnitude of the streaming potential field induced by the pressure-driven flow. Furthermore, it was found that the flow rate in a curved microtube could be larger than that in a straight one with the same pressure gradient and shape of cross section. The study also suggested that the curved geometry could be beneficial to improving the electrokinetic energy conversion efficiency.