Noninvasive Glucose Sensors Using Defective-Ground-Structure Coplanar Waveguide

Abstract

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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$22\times12$ </tex-math></inline-formula> mm with a sample holder realized by the 3-D printing technology. Experiments demonstrate that the frequency sensitivity is about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.852\times 10^{-{5}}$ </tex-math></inline-formula> GHz/(mg/dL) and the amplitude sensitivity is close to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${6.54} \times {10}^{-{4}}$ </tex-math></inline-formula> dB/(mg/dL). On this basis, the array structure is repeated five times to expand the sensing area, leading to a frequency sensitivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.9\times 10^{-{6}}$ </tex-math></inline-formula> GHz/(mg/dL) and an amplitude sensitivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5\times 10^{-{3}}$ </tex-math></inline-formula> 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.