Compact Instrumentation for Accurate Detection and Measurement of Glucose Concentration Using Photoacoustic Spectroscopy

Abstract

In this work, a novel <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">compact</i> and accurate glucose concentration measurement system is developed using the well-established photoacoustic Near Infra-Red spectroscopy. The proposed <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in-vitro</i> instrumentation methods are in a small form factor, making it a viable candidate and precursor for an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in-vivo</i> non-invasive <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">wearable</i> 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 xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$ </tex-math></inline-formula> 10.65mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <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 xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <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 xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">compact</i> form, with lock-in amplifier and aided with machine learning algorithms for future application as a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">wearable</i> device.