Mixers used in the microdevices can be categorized as active or passive. Active mixers utilize external energy (i.e. pressure, electrokinetic disturbance etc.) for mixing and inducing transverse flow. On the other hand, diffusion or chaotic advection is the dominant mixing mechanism in passive mixers. The most basic passive micro-mixer is a T-mixer or Y-mixer, where two different solutions flow adjacently in the same direction and mixing is primarily due to diffusion in the transverse direction. There are various modifications reported in the literature for enhancing mixing performance for T-mixers. Some of reported approaches include sequential injection of samples, patterned heterogeneous surface charge along the walls, grooved patterns on the channel base, etc.

In this numerical study, we present a novel micro-mixer design which utilizes the recent concept of induced charge electro-osmosis (ICEO) for enhancing mixing performance in a T-mixer. Any external electric field will induce charges on the metal surface which in turn leads to the formation of an electric double layer (EDL) around the metal surface. The electric field will then act on the diffuse part of the EDL to generate different kinds of flow pattern within the micro-channel. In this particular case, micro-vortices can be generated using ICEO, which enhances the mixing performance in the device. The proposed mixer design is compared with the traditional mixer design and found to be superior in terms of performance. The numerical results are found to be in agreement with analytical results available for electrokinetic flow and electrokinetic mixing for the conventional T-mixer. Further, the effect of design and operational parameters on the mixing performance is analyzed for the new design.