Particle experiments
Different diameters of fluorescently labelled, neutrally buoyant
polystyrene particles from ThermoFischer Scientific of 10µL were spiked
into 10 mL of 150 ppm concentration polyethylene oxide (PEO), Molecular
weight = 2,000 kDa and was used as a sample fluid. PEO of same
concentration without polystyrene particles were used as sheath fluid.
Different sized particles such as 1, 3, 5 and 7 µm from the same company
were used for particle experiments. A Harvard Apparatus Pump 33 DDS
syringe pump was used to pump the sample and sheath flowing from a 20 mL
BD plastic syringes. The syringes were connected to the inlets and
outlets of the chip using COLE-PARMER TYGON tubing with inner diameters
of 0.254 mm and outer diameter 0.762 mm. The migration and focusing of
particles in the microchannels was observed using AXIOVERT 135 TV
inverted fluorescence microscope. The sample flow rate for all
experiments was kept at 50 µL/min. The sheath flow rate was varied based
on the experiment. Fluorescent quantification was performed using ImageJ
freeware (https://imagej.nih.gov/ij/).