A 1 ml solution of 0.1% 10 um biotinylated polystyrene microspheres was injected at 2 ml / min through a transparent chamber formed around the well of a classical FPW device.  A standing acoustic field in chamber trapped a portion of these beads.  Photos of these trapped spheres taken with visible light are shown below.  A 1 ml solution of Alexa-Fluor 488 labeled streptavidin was perfused through the chamber at 33 ul/min.  Unconjugated streptavidin was purged from the chamber with phosphate buffer.  The streptavidin-biotin conjugate was detected with a Zeiss Stereoscopic Epifluorescent Microscope.  Fluorescent images are given below.
 
 
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