  This report introduces a novel optofluidic platform based on piezo-MEMS
technology, capable of identifying subtle variations in the fluid
concentration. The system utilizes piezoelectric micromachined ultrasound
transducers (PMUTs) as receivers to capture sound waves produced by nanosecond
photoacoustic (PA) pulses emanating from a fluid target housed in PDMS
microchannels. Additionally, a dedicated low-noise single-channel amplifier has
been developed to extract the minute analog voltage signals from the PMUTs,
given the inherently weak ultrasound signals generated by fluid targets. The
PMUTs' proficiency in detecting changes in fluid concentration under both
static and time-varying conditions has been documented and verified, confirming
the platform's efficacy in monitoring fluid concentrations.
