Research On Side-polished Optical Fiber SPR Sensor For Blood Glucose Concentration Measurement With Temperature Compensation

Blood glucose detection is is one of the important items in people’s daily health management.In recent years,non-invasive blood glucose detection technology has been widely concerned by scholars from all walks of life.It is generally calibrated by measuring the glucose concentration in the saliva of the body on an empty stomach,the amount of tissue fluid it extracts needs to be diluted,so the sensor needs to be sensitive to very low glucose concentrations.Therefore,it is necessary to propose a sensor with high sensitivity and can monitor temperature change simultaneously.Optical fiber surface plasmon resonance(SPR)sensor to avoid,as a high-accuracy,label free detection technology,has been widely applied in biomedicine and other fields.This thesis proposed side polished fiber(SPF)combined with SPR,based on fiber Bragg grating temperature measurement principle,a side polished fiber surface plasmon resonance(SPF-SPR)sensor with temperature self compensation is proposed to detect glucose concentration.The common optical fiber SPR structure is less sensitive and is easily disturbed by ambient temperature,but this sensor fully releases the evanescent field in the optical fiber,and the sensitivity is higher.The polishing plane is the sensing area,which is easy to modify the biomolecular sensitive layer on the optical fiber surface,so as to improve the detection precision and speed of the sensor.At the same time,the integration of fiber Bragg grating(FBG)can automatically compensate the drift of SPR spectrum caused by temperature and improve the accuracy of system measurement.This project has completed the following research work:Firstly,the design of SPF-SPR sensor is proposed.The basic principle and sensing characteristics of optical fiber SPR sensor are studied.The SPF is combined with SPR,a side polished fiber SPR model;simulation and optimization of the structure parameters of the sensor,metal film type,SPF-SPR sensor optimal metal film thickness,to determine the sensor length and fiber grinding residual thickness.To achieve low glucose concentration measurement,the glucose oxidase sensitive membrane is modified on the sensing area,which can specifically bind to the glucose molecules and improve the detection accuracy.Secondly,the theoretical analysis of the temperature characteristics of the sensor is carried out.Two schemes of temperature compensation are proposed which are cascaded Prague fiber Bragg grating(FBG)and cascaded long period fiber grating(LPFG).The temperature sensing characteristics of the two kinds of gratings are analyzed.The influence of the length of the two gate and the grating period on the sensing performance is studied.The temperature and refractive index sensitivity of the two kinds of gratings are calculated by simulation.The separability of the two parts of the SPF-SPR and FBG is analyzed,which provides a feasible basis for the realization of temperature compensation.Thirdly,the processing method of side polished fiber is studied.The SPF is made by using the arc groove base block polishing method and the wheel polishing machine respectively.The process of chemical wet plating of silver film and surface modified glucose oxidase(GOD)biosensitive layer was investigated.In order to prevent the inactivation of GOD by silver particles,graphene oxide is used as the transition layer.Fourth,test the performance of the sensor.The sensitivity of glucose concentration detection before and after GOD modification was compared.In the range of glucose concentration of Omg/dL～200mg/dL,there is a good linear relationship between the resonant wavelength and the concentration of the sensor.The sensitivity of the test is 0.0572nm/mg·dL-1,which is about 6 times higher than that of unmodified.At the same time,the stability test results of the sensor are better,and the standard deviation of the glucose concentration single point measurement is less than 10-3.The temperature compensation cross measurement experiment is carried out on the sensing system.The effect of cascaded LPFG and FBG on the post spectrum was compared,and then the temperature compensation was selected by using FBG.The sensor effectively solved the cross sensitive problem of temperature and concentration,and realized the simultaneous measurement of glucose concentration and temperature.