Glucose aqueous solution sensing by a near-field microwave microprobe

We observed the glucose concentration of solutions using a near-field microwave microprobe (NFMM). Instead of the usual technique, we take advantage of the noncontact and label-free evaluation capabilities of a NFMM. A NFMM with a high Q dielectric resonator allows observation of small variations of the relative permittivity due to changes in the glucose concentration. By measuring the reflection coefficient S11 at an operating frequency near 4.5 GHz, we could observe the concentration of glucose with a detectable resolution of 0.5 mg/ml (0.05%). A glucose biosensor using a NFMM provides a unique approach to monitor glucose concentration.