Simulation tool for the prediction of compound dependence of CW-photoacoustic-based sensor using dual optical excitation

Towards the development of a sensor dedicated to noninvasive and continuous blood glucose level monitoring, we developed a protocol called optical power balance shift (OPBS) based on a continuous-wave photoacoustic technique using a dual wavelength excitation sequence. In order to optimize the sensor response, we showed, using an analytical model, that the OPBS response depends exclusively on the absorption coefficients at the two wavelengths. Then, using a standard near-infrared spectrophotometer, we measured the absorption coefficient of water as well as the fractional absorption coefficient relative to glucose and albumin concentrations and temperature. We then plotted the OPBS-based sensor response for the three aforementioned parameters covering all the possible combinations of the two wavelengths from 1300 to 2500 nm. Despite overall similar tendencies, the responses exhibit highs and lows at optical pairs specific to each compound, which allow potential improvement of measurement specificity to one compound in particular by choosing the appropriate pair of optical wavelengths. The good agreement between the model and experimental results for the 1610/1382-nm combination validates the approach.