Enhanced microparticle focusing in a serpentine microchannel integrated on a lab-on-a-disk platform using combined inertial and dielectrophoretic forces
Mahdi Zare, Mahdi Khatibi, Seyed Nezameddin Ashrafizadeh, Jérôme F. L. Duval
Abstract
Precise focusing of microparticles is a key issue in microfluidic systems, playing a key role in applications such as particle separation, cell sorting, biomedical diagnostics, and lab-on-a-chip technologies. Achieving high-particle separation efficiency with minimal focus width remains a significant challenge in this field. Among various designs, serpentine microchannels are widely employed to induce secondary flows, particularly Dean flow. In this work, formalism was developed and simulations conducted in a serpentine microchannel integrated in a lab-on-disk (LOD) platform to leverage rotational forces—including centrifugal and Coriolis forces—alongside Dean flow and enhance particle focusing, taking macrophage cells as a model system. To further refine and improve cell focusing, multiple electrodes were incorporated to generate an electric field, introducing a dielectrophoretic (DEP) force to the process. Numerical simulations were conducted to analyze the effects of key parameters on fluid flow profiles, including flow rate (u), number of microchannel turns (UN), rotation speed and angular velocity (ω), configuration and number (Ne) of electrodes, frequency of applied field (f), and applied voltage (V). The governing Navier–Stokes equations for fluid flow, the equation of rotational motion, and the continuity equation for flow density were implemented to model particle behavior within the system. The results demonstrated that increasing the number of turns and the applied field voltage significantly enhanced process performance. At UN = 15 and/or V = 200 V, about 100% of the particles exited through a single outlet, while the focusing width (Wf) was reduced from 90 to 13.8 μm and 6.6 μm, respectively. Additionally, the optimal system parameters were determined as u = 0.025 m/s, ω = 100 rad/s, f = 100 kHz, and Ne = 12. This study highlights the synergy between inertial forces and DEP in LOD platforms, demonstrating its potential for high-precision particle manipulation, including sorting, focusing, and cell separation applications.