Experimental Based Blood Glucose Monitoring with a Noninvasive Cylindrical Biosensor

Abstract

In this work, we have designed and fabricated a noninvasive flexible biosensor with a simple and printable structure for blood glucose monitoring. The proposed sensor has been experimentally proven to monitor blood sugar levels through frequency shifts. A cylindrical design with a coplanar waveguide (CPW) feeding technique has been proposed. A targeted frequency of 2.4 GHz with the best S11 at −22.623 dB and a bandwidth of 323 MHz was obtained. However, after propagating through the finger phantom, the signal is sensitive to the blood glucose levels with a significant frequency shift. The biosensor worked well at 1.55–1.88 GHz, representing a finger, without a phantom in the ISM band of 2.4 GHz. There is a bit of shifted frequency during the biosensor measurement with less than a 1.41% error. The overall size of the biosensor is 50.66 mm × 60.31 mm. The biosensor uses a flexible Dupont Pyralux substrate; thus, the index finger is easy to insert. 25 volunteers were involved in this experimental blood glucose. For this, we use an invasive device to measure the volunteers’ blood glucose levels. The invasive measurement results obtained are used as a reference for the blood sugar levels of each sample. The test results using a cylindrical biosensor show a frequency shift at 7.5 MHz for every mg/dl of blood sugar levels, with a sensitivity of 0.43 1/(mg/dL). This frequency shift can be used to observe changes in the concentration of sugar levels in the blood. This flexible sensor is a good alternative biosensor for measuring blood glucose levels due to its low cost and printable structure.