All-optical splitting of dielectric microdroplets by using a y-cut-LN-based anti-symmetrical sandwich structure.

We demonstrate an all-optical active mode of dielectric microdroplet splitting in a sandwich structure consisting of two anti-symmetrical y-cut LN:Fe substrates. The dynamic process of the microdroplet splitting and the simulation of the electrostatic interaction inside the sandwich gap show that the combination of two anti-symmetrical substrates are capable to provide a sufficient dielectrophoretic force and to reduce the unbalance of the drag forces for a stable and efficient splitting of the microdroplet. The dependences of the splitting time on the illumination intensity and the initial microdroplet size are also studied, and the results show that the microdroplet splitting process is fully governed by the establishment of the superposed photovoltaic field inside the sandwich gap. A key ratio Er/E0, representing the microdroplet splitting difficulty for a given sandwich structure, is found linearly dependent on the initial microdroplet size. These points are quite important to the integration of splitting functionality on the LN-based microfluidic chip.