Non-invasive in vitro sensing of D-glucose in pig blood.

We have developed an electromagnetic resonant spiral sensor and have measured the glycemia in pig blood and the concentration of D-glucose in aqueous solution by using a real-time electromagnetic interaction phenomenon between the microwave sensor and the liquid. We could determine the concentration of glucose with a minimal resolution of 5 mg/dl in the 100-600 mg/dl concentration range at operating frequencies of about 7.65 GHz (for the glucose aqueous solution) and 7.77 GHz (for the pig blood sample). The change in the glucose concentration brings the changes of the microwave reflection coefficient due to the electromagnetic interaction between the resonator and the glucose solution. The in vitro results show the measured signal-to-noise ratio of about 34 dB, and the minimum detectible signal level of about 0.022 dB/(mg/dl). Our proposed system provides a unique approach for non-invasive and non-contact glucose monitoring, and it may serve as a bloodless glucometer.