Mixing Enhancement in Microfluidic Devices Using Contactless Dielectrophoresis (cDEP)

Rapid mixing is necessary in lab-on-a-chip (LOC) and Micro Total Analysis Systems (μTAS) devices for chemical and biological processes [1]. Because of the small length scale of microdevices, rapid efficient mixing is difficult to achieve. Thus mixing without any intentional stretching and folding of interfaces is dominated by molecular diffusion, which takes a long time relative to the typical operating timescale of these microdevices. To address this need, various techniques for enhancing mixing in microdevices have been proposed [1]. Electrokinetic mixing has proven to be an efficient method for actively mixing solutions or microparticles [2]. Among electrokinetics techniques, DEP, the motion of a particle in a suspending medium due to the presence of a non-uniform electric field [3], has shown a great potential for particle separation, manipulation, and identification. However, there is not much reported use of DEP for mixing enhancement reported in the literature. Lee et al. [4] presented a micromixer that uses DEP force to generate chaotic trajectories within a mixing chamber. Although DEP has been a very successful technique to manipulate microparticles, it has some drawbacks such as electrolysis (bubble formation), electrode delamination and sample contamination.