Photoacoustic spectroscopy that uses a resonant characteristic of a microphone for in vitro measurements of glucose concentration.

Glucose measurements using photoacoustic spectroscopy have been highlighted to be a modality for non-invasive glucose monitoring. Previous photoacoustic spectroscopy for glucose measurements have used a resonant acoustic cell with a broadband capacitive microphone to increase sensitivity. However, a resonant characteristic of a microphone has not been investigated yet due to the working frequency range much lower than the resonance frequency of the microphone membrane. We, here, present a photoacoustic spectroscopy system that utilizes an ultrasound resonance of a microphone to increase sensitivity. We found that matching the resonance of a photoacoustic cell with the resonance of a microphone can increase signal-to-noise ratio and our system can distinguish the glucose concentration in liquid.