The separation and manipulation of microparticles in lab on a chip devices have importance in point of care diagnostic tools and analytical applications. The separation and sorting of particles from biological and clinical samples can be performed using active and passive techniques. In passive techniques, no external force is applied while in active techniques by applying external force (e.g. electrical), higher separation efficiency is obtained. In this article, passive (pinched flow fractionation) and active (insulator-based dielectrophoresis) methods were combined to increase the separation efficiency at lower voltages. First by simulation, appropriate values of geometry and applied voltages for better focusing, separation, and lower Joule heating were obtained. Separation of 1.5 and 6 μm polystyrene microparticles was experimentally obtained at optimized geometry and low total applied voltage (25 V). Also, the trajectory of 1.5 μm microparticles was controlled by adjusting the total applied voltage.

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A coupled optical-electrical-thermal modeling has been developed to investigate the heat generation in CZTSSe solar cells via Thermalization, Joule heat, Peltier heat, Surface Recombination heat, and non-radiative recombination heat and also the heat dissipation via convective and radiative cooling. These were calculated and displayed in 2D and 3D maps either at zero bias or open-circuit voltage (V oc) conditions. At V=0, the heat is generated mainly at the junction of CZTSSe/CdS where the thermalization and Joule heats are dominantly higher compared to non-radiative (SRH and Auger) recombination heat. However, at V=V oc , the nan-radiative recombination heat becomes comparatively higher than the Joule heating whereas the thermalization remains highest as before. Apart from the bulk heating factors, we also studied the surface recombination and Peltier heat generation. The surface recombination heat is higher at V=V oc compared to at V=0 while the Peltier heat is zero at V=V oc which can be explained by looking at the energy band diagrams at these voltages. The total heat generation does not change much across the cell thickness (<5×10 9 W/m 3) as the cell is quite thin. Nevertheless, the individual impact of every heat generation factor on power-density and current-voltage characteristics of the cell reveals that the thermalization, Joule, and non-radiative recombination heats reduce the open-circuit voltage of the cell from 0.54 V to 0.49 V (∆V = 0.047 V) while the Peltier and surface recombination heat is less effective. The temperature of the cell shows a small distribution across the cell (0.01 K). However, the temperature of the initial study at 293 K increases to 315-320 K for the coupled study. At this increased temperature, the short current-density doesn’t change but the fill factor decreases from 73.8% to 71.8% and, therefore, the energy conversion efficiency of the cell falls by 11.11% (from initial 12.78% to 11.36%). All the total heat dissipation, convective, and radiation cooling follow a similar trend to the total heat generation but convective cooling is the dominant component of dissipation.

Focusing and separation of microparticles in a complex mixture have had wide applications in chemistry, biology, medicine, etc. This work presents a numerical and experimental investigation on focusing and continuous separation of microparticles in a geometrically optimized arrangement of steps in the form of a staircase using insulator-based dielectrophoresis (iDEP) mechanism. First, a detailed finite element analysis was performed on important parameters in the focusing and separation of microparticles, such as geometry of stair-shaped microchannel, total voltage, and voltage difference applied to reservoirs. The optimum parameters obtained from numerical analysis were used for experimental work. Theoretically, predicted microparticle trajectories are in good agreement with experimentally observed ones. Experimental and numerical results show that the performance of focusing of microparticles enhances with growth of the total voltage (in a constant voltage difference) and decreases with voltage difference. The fabricated iDEP microchip enhances the performance of focusing and separation of microparticles due to its stair-shaped microchannel and therefore operates at low DC total applied voltages of 90-110 V.