High-speed discrimination and sorting of sub-micron particles using a   microfluidic device
  The size- and fluorescence-based sorting of micro- and nano-scale particles suspended in fluid presents a significant and important challenge for both sample analysis and for manufacturing of nanoparticle-based products. Here we demonstrate a disposable microfluidic particle sorter that enables high-throughput, on-demand counting and binary sorting of sub-micron particles and cells, using either fluorescence or an electrically-based determination of particle size. Size-based sorting uses a resistive pulse sensor integrated on-chip, while fluorescence-based discrimination is achieved using on-the-fly optical image capture and analysis. Following detection and analysis, the individual particles are deflected using a pair of piezoelectric actuators, directing the particles into one of two desired output channels; the main flow goes into a third waste channel. The integrated system can achieve sorting fidelities of better than 98\%, and the mechanism can successfully count and actuate, on demand, more than 60,000 particles/min. 
Sukumar Rajauria, Christopher Axline, Claudia Gottstein, and Andrew N.   Cleland
cond-mat.soft physics.ins-det