| Summary: | In this work, a novel <italic>compact</italic> and accurate glucose concentration measurement system is developed using the well-established photoacoustic Near Infra-Red spectroscopy. The proposed <italic>in-vitro</italic> instrumentation methods are in a small form factor, making it a viable candidate and precursor for an <italic>in-vivo</italic> non-invasive <italic>wearable</italic> blood glucose monitoring in the near future. The accuracy comes from the phase sensitive detection of the electrical signal. This detection technique uses an off-the shelf modulator/demodulator integrated circuit configured as a lock-in amplifier to increase the signal to noise ratio multifold. No prior work on photoacoustic spectroscopy, has taken advantage of this detection methodology in such a small form factor. The dimension of the lock-in-amplifier is 13mm <inline-formula> <tex-math notation="LaTeX">$\times$ </tex-math></inline-formula> 10.65mm <inline-formula> <tex-math notation="LaTeX">$\times$ </tex-math></inline-formula> 2.65mm. The maximum linear dimension of the exciting laser is 5.6 mm. The acoustic sensor (transducer) has a dimension of 42mm <inline-formula> <tex-math notation="LaTeX">$\times$ </tex-math></inline-formula> 12mm. Furthermore, the measurement and analyses of the observed data uses multiple stochastic and machine learning techniques to bring out the best correlation fit between the glucose concentration and a specific feature of the electrical signal. With these methods and techniques, a strong correlation was confirmed between the glucose concentration and the amplitude of the electrical signal. The computed correlation coefficient between the signal amplitude and glucose concentration is 97% while the p-value is 5.6E-6. To the best of our knowledge, this is the first work to report photoacoustic spectroscopy for glucose concentration measurement in a <italic>compact</italic> form, with lock-in amplifier and aided with machine learning algorithms for future application as a <italic>wearable</italic> device.
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