Abstract
Optically-induced dielectrophoresis (ODEP) has been demonstrated to generate virtual electrodes for manipulating particles/cells by illuminating a light pattern on photoconductive materials. Because the production of the ODEP force requires a solution that has suitably low conductivity and appropriate dielectric constant; currently 0.2M sucrose is used. However, it requires a complicated medium replacement process before one could manipulate cells. We traditionally centrifuged cells several times for the complete replacement of the medium from the culture medium to 0.2 M sucrose. It is a complex and time-consuming operation, and the repeated replacement process can easily lead to cell contamination problems. Furthermore, 0.2M sucrose is not suitable for the long-term viability of cells. In this work, we demonstrated an integration of a microfluidic device with an ODEP device such that the critical medium replacement process can be automated and the cells could be subsequently manipulated by using optical images. In comparison to conventional manual processes, the automated medium replacement process only took25 minutes. There was up to a 91% recovery rate of cells, and a 109.1μm/s dragging velocity was induced by ODEP. More importantly, the survival rate of cells could be greatly enhanced due to the faster automated process. The new, integrated microfluidic chip could automate the entire process of medium replacement without the contamination issue. It is then concluded that the developed microfluidic system may provide a platform for fast replacement of cell medium. It is also the first time that an ODEP device was integrated with microfluidic devices. By achieving automated and fast medium replacement, this device can be deployed for a wide range of ODEP-based sample pre-treatment processes while improving cell viability after completing the experiment. With further developments, this device may contribute to the area of ODEP-based cell manipulation.