Sample transport and electrokinetic injection in a microchip device for chemical cytometry.

Sample transport and electrokinetic injection bias are well characterized in capillary electrophoresis and simple microchips, but a thorough understanding of sample transport on devices combining electroosmosis, electrophoresis, and pressure-driven flow is lacking. In this work, we evaluate the effects of electric fields from 0 to 300  V/cm, electrophoretic mobilities from 10(-4) to 10(-6)  cm(2)/Vs, and pressure-driven fluid velocities from 50 to 250  μm/s on sample injection in a microfluidic chemical cytometry device. By studying a continuous sample stream, we find that increasing electric field strength and electrophoretic mobility result in improved injection and that COMSOL simulations accurately predict sample transport.