Non-invasive blood sugar detection by cost-effective capacitance spectroscopy

Capacitance spectroscopy is a promising technique for detecting small changes in electrical properties of human blood such as conductivity, permittivity, capacitance, and dielectric constant due to the change of glucose concentration. We studied the capacitance of tissue-mimicking phantoms and the human body, in vitro and in vivo, for detecting blood sugar levels non-invasively by a simple and cost-effective setup. We found that, in tissue-mimicking phantoms, capacitance decreased similar to 19 % for glucose concentration increases of 85 % with a correlation coefficient of R-2=0.96. In the oral meal tolerance test (OMTT), the body capacitance increased less than 9 % for a 50 % increase in blood sugar level, and it followed the invasive reference with a lag time of similar to 25-45 min and semi-invasive reference with a nominal time delay. This lag time is associated with the food digestion time and the diffusion time for the glucose to reach interstitial fluid from blood vessels. We also studied different types of metal pads made of copper, gold-coated copper, and aluminum with various sizes for system optimization. Considering the simplicity, low cost, easy operation, and moderate performance, this capacitive spectroscopy could potentially be a promising technique of detecting blood sugar levels and could be incorporated into other blood sugar detection techniques to reinforce the overall performance.