A particle-capturing and -separating, sheathless chip in series with microfilters and planar interdigital electrodes

Abstract Research on microfluidic chips is becoming more and more important in life sciences, medical testing, and chemical reactions. In the process of separating particles by dielectrophoresis (DEP), focusing of mixed particles is essential. The commonly used focusing method is sheath flow which dilutes the particle samples. However, it requires an additional injector which precludes development of an integrated system for chemical analysis and biological detection. In this paper, we propose a novel sheathless, shunt-focusing approach using microfilters (MFs) and interdigital electrodes to achieve particle capture and separation. By passing through a shrinking channel, most of the flowing small particles pass through the MFs, generating an artificial sheath flow in the channels to achieve focusing. Subsequently, interdigital electrodes provide DEP force to separate the particles. Separation efficiency was assessed by collecting polystyrene (20 μ m diameter) from silica (4 μ m diameter) at various flow rates. From the experimental results, the efficiency of capture reached 71%–86% and that of separation was over 98.6%. This chip is expected to be applied to the separation of circulating tumor cells in blood samples.