Sheathless focusing

To overcome these limitations imposed on conventional and microfluidic methods for size separation, hydrophoretic methods have been developed. Here we provide a review of the methods for continuous size separation of microparticles, blood cells and cell-cycle synchrony, and for sheathless focusing of cells without external fields and sheath flows in microfluidic devices. We describe details of the separation mechanism and its application to particle and cell manipulation, comparing its advantages and disadvantages with other microfluidic methods. Finally, we present some challenges of the hydrophoretic technology. 

S. Choi, S. Song, C. Choi and J.-K. Park, Sheathless focusing of microbeads and blood cells based on hydrophoresis, Small, 4, 634-641 (2008). 

Goddard G, Martin JC, Graves SW, Kaduchak G (2006) Ultrasonic particle-concentration for sheathless focusing of particles for analysis in a flow cytometer. Cytometry A 69 66-74... 

CE provides a complementary approach to HPLC separation. It is performed in several different formats, including capillary zone electrophoresis, miceller electrokinetic chromatography, capillary gel electrophoresis, capillary isoelectric focusing, isotachophoresis, and capillary electrochromatography. Of these formats, capillary zone electrophoresis is the most popular separation technique. The most successful coupling of CE with mass spectrometry is achieved via an ESI interface. The three most practical designs are sheathless interface, sheath-flow interface, and liquid-junction interface. 

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