Fig. 3.

(a) A schematic diagram of the imaging system. PA, power amplifier; FG, function generator; PDG, pulse delay generator; UST, focused ultrasound transducer; PMT, photomultiplier. (b) A representation of the $2\mu \mathrm{s}$ integrator gate window that was overlaid with the UMF signal. The green line represents the donor and the red dashed line represents the acceptor. (c) A fluorescent image of a single microbubble. (d) A fluorescent image of diluted microbubble solution flowing inside of the $500\text{-}\mu \mathrm{m}$ polydimethylsiloxane (PDMS) microchannel.