Minimally-invasive body-fluids analyzer for continuous glucose monitoring

Summary form only given. Efficient management of blood glucose (BG) levels in diabetic patients relies heavily on accurate and frequent analysis of BG levels. Therefore, detection techniques (direct or indirect) that can provide reliable measurements of BG levels are of utmost interest. In a typical integrated analytic device, sampling (most utilized are the lancing devices) is a painful experience for patients that require frequent finger-prick to draw a minimal volume of blood for analysis. Besides the unpleasant experience, drawing blood is a source of contamination and/or transfer of blood-borne infections. Microneedles is one of the great candidates for minimally invasive BG level monitoring. One type of microneedles is the hollow one which is used to extract small samples of blood or body interstitial fluids to measure the BG level. A second type of microneedles is used to probe the impedance of the blood to indirectly measure the BG level. We designed a new miniature attenuated total reflectance-Fourier transform infrared spectrophotomer for body-fluids analysis. The key component of the system is the microneedle used to probe and detect the BG level either directly or indirectly (interstitial fluid sampling). Our approach will exploit established infrared spectrophotometry technology in a new design of the probe element for spectral analysis. We designed and simulated the microneedle shown in the figure that analyzes blood or interstitial fluid at the site of stinging and directly on the surface of the microneedle. Full 2-D optical analysis using Comsol software is performed. The microneedle is excited from its top tapered side by a normal incident of a Gaussian beam. The beam will propagate inside the microneedle, which will encounter multiple reflections from the microneedle surface in contact with the interstitial fluids and will return back to the same tip of the microneedle. The other side is plated with metallic reflective layer to fully reflect the incident Gaussian beam back to exit from the same tip of the microneedle. The reflected Gaussian beam with a reference beam will constitute an interferogram from which the signature of the glucose is mathematically extracted. The fabrication process of the microneedle is a simple three masks process composed of wet and deep reactive ion etching of the device layer of an SOI wafer.