Numerical model of the sorting of biological cells based on gravity-driven optoelectronic tweezers

Novel gravity-driven optoelectronic tweezers were developed for accurately sorting Jurkat and B16 cells. Synergistic integration of gravity and optoelectronic tweezers was developed as a new tool to provide unique features for sorting or separating mixtures of cells with different dielectric properties. This chip combined flexible programmable virtual electrodes with gravity-driven hydrodynamic flow motion instead of complicated fabrication of micro-pumps and valves. Accordingly, the structure of the microchannel was dimensional, based on a theoretical analysis and numerical model. Using both Jurkat and B16 cells, we obtained the dielectrophoretic separation frequency by using a single-shell model, reflecting their effective complex permittivity. Finally, the results of cellular trajectory analysis demonstrated that the gravity-driven optoelectronic tweezers were able to achieve sorting of Jurkat and B16 cells at a voltage of 11 V with 221.5 kHz, based on a molecular dynamics approach. To further enhance the separation accuracy and reduce the risk of lysing membranes, improved microchannels with two separated branches were designed and studied. Additionally, the shape of the virtual electrode was optimized to generate a greater electrical field magnitude than a rectangular electrode. Thus, the applied electrical voltage could be reduced to 7 V for cell sorting.