Noninvasive Glucose Sensors Using Defective-Ground-Structure Coplanar Waveguide

A noninvasive glucose sensor using defective-ground-structure (DGS) coplanar waveguide (CPW) transmission line is proposed for the first time. The device operates as a microwave resonantor, which is affected by glucose concentration. The size of the fabricated DGS sensor is
$22\times12$
mm with a sample holder realized by the 3-D printing technology. Experiments demonstrate that the frequency sensitivity is about
$1.852\times 10^{-{5}}$
GHz/(mg/dL) and the amplitude sensitivity is close to
${6.54} \times {10}^{-{4}}$
dB/(mg/dL). On this basis, the array structure is repeated five times to expand the sensing area, leading to a frequency sensitivity of
$3.9\times 10^{-{6}}$
GHz/(mg/dL) and an amplitude sensitivity of
$5\times 10^{-{3}}$
dB/(mg/dL). The array DGS sensor sacrifices frequency sensitivity but improves the amplitude sensitivity by a factor of 7.65 compared to the single-structure device. The proposed sensor may have a good application prospect for human health monitoring in future.