Abstract
Fiber-based techniques make it possible to implant a miniaturized and flexible surface plasmon resonance (SPR) sensor into the human body. However, for implantable applications, the miniaturization of fiber SPR sensors results in low sensitivity compared with traditional prism-type SPR sensors due to limited space and the effects of temperature fluctuations. Therefore, it is necessary to compensate for temperature drift in the measurements, such as the case of the quantification of the relationship between glucose concentration and SPR resonance wavelength. In this report, we proposed a highly sensitive fiber SPR sensor based on a side-polished structure modified by graphene for implantable continuous glucose monitoring with in situ temperature self-compensation using a long-period fiber grating (LPFG). The results demonstrate that the sensor with monolayer graphene achieved the best sensitivity of 3058.22 nm/RIU, and the LPFG achieves a maximum resolution of 0.042 nm/°C. The proposed SPR sensor enabled the detection of hypoglycemia, which is still a significant challenge for continuous glucose monitoring in a clinical setting.
Highlights
Diabetes mellitus is a common chronic disease that requires continuous monitoring of blood glucose level to provide guidance for diagnosis and therapy [1,2]
Glucose determination based on refractive index variation guarantees that no glucose is depleted during the measurement process which is critical in the detection of hypoglycemia, which is still a significant challenge with regard to continuous glucose monitoring using an enzyme electrode sensor [6]
The light from a supercontinuum white laser source is coupled into the core of the proposed fiber surface plasmon resonance (SPR) sensor
Summary
Diabetes mellitus is a common chronic disease that requires continuous monitoring of blood glucose level to provide guidance for diagnosis and therapy [1,2]. Graphene has attracted great attention because of its distinctive electrical and optical properties [12,13] It can significantly increase the mobility of electrons on the gold film of the SPR sensor, since the charge carrier mobility of graphene is reported to be as high as 106 cm V−1 s−1 and it is known as the best conductor to date [12,14]. Based on the remarkable properties of graphene, we designed a high sensitivity fiber SPR sensor with a side-polished structure for easy modification of CVD graphene, which can promote the electron mobility of gold and the adsorption of a glucose molecule to achieve high sensitivity of refractive index-based detection [18]. We engraved the LPFG onto the fiber core to incorporate a temperature sensor inside the SPR sensor such that in situ temperature and concentration can be obtained simultaneously to compensate for the temperature drift of the SPR spectrogram
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