  Opto-mechano-fluidic resonators (OMFRs) are a new platform for
high-throughput sensing of the mechanical properties of freely flowing
microparticles in arbitrary media. Experimental extraction of OMFR mode shapes,
especially the acoustic pressure field within the fluidic core, is essential
for determining sensitivity and for extracting the particle parameters. Here we
demonstrate a new imaging technique for simultaneously capturing the spatially
distributed acoustic pressure fields of multiple vibrational modes in the OMFR
system. The mechanism operates using microparticles as perturbative imaging
probes, and potentially reveals the inverse path towards multimode inertial
detection of the particles themselves.
