OpticalFluorescenceandItsapplicationtobloodglucosemonitor

1、Optical Fluorescence and Its application to blood glucose monitorPan Yongfeng(Wuhan University of Technology, Wuhan, China, xhyzjiji)AbstractBlood glucose monitor system is designed with the core of photonic crystal fiber (PCF) and technology of small invasive photoelectric. According to the princip

2、le that different blood glucose concentration absorbs different light, optical modulation is controlled by MSP430 Light is emited to the blood samples through transmission of three probe fiberoptic sensor. The reflected light is inputed to MSP430 after photoelectric conversion. Blood glucose concent

3、ration is calculated after A/D conversion. The system has characteristics of easyoperation, low energy.Keywords photonic crystal fiber(PCF); smallinvasive; blood glucoseI. I NTRODUCTIONith the rapid development of science and technology, optical fiber has increasingly expanded in the medical, commun

4、ications, W electronics and electricity, and other fields. It is becoming the basis of promising materials. In practice, however, the optical fiber, as a transmission medium to wire will inevitably need to be bended. When traditional optical fibers are of bending, bending loss will affect the signal

5、 transmission properties and sensitivity. Photonic crystal fiber (photonic crystal fiber, PCF) is a new type of optical fiber, which is formed by a single medium, clad in two-dimensional photonic crystals structure. It is different from the traditional optical fiber because of its small bending loss

6、, Optical fiber features stable etc. Based on this, the blood glucose monitor system use PCF as optical waveguide materials and designe the three probe beam PCF sensor to monitor blood glucose. The system has high precision, low cost, good portability.II.D ESIGN PRINCIPLESA. Measuring principleThe g

7、lucose in the blood will be oxidated and finally turn into delta-gluconolactone by GOD, when the blood sample drops into the test paper which contains oxidase for the oxidation of glucose. This substance reacts with peroxidase in the reagent, and thenwill generatea light-absorbingmaterial. Weplace t

8、he paper in the reflectiveintensity modulation typefiber opticsensor in theoptical path, as shown in figure 1. The whole sensor system includes a light source, optical fiber, optical fiber and optical detectors.The light emitted by light source reach the surface of blood sample through the filter an

9、d transmitting fiber. Due to material suctionlight modulation,reflected light withblood sugar informationwillbe received by receiving optical fiber,finallyturned intoelectrical signals by the photoelectric receiver converts. When the power of light source and optical fiber probe and the distancebetw

10、een the reflective surfaces remain unchanged, the receiving optical fiber receives a certain wavelength of light intensity and thewavelength of incident light intensity is the ratio of the corresponding relationship with blood sugar levels. According to the lightintensity of the signal, the blood gl

11、ucose concentration can be calculated. But the main drawback of this kind of optical fiber sensoris measurement error caused by light source, optical power changes when light excitation is not stable. In addition, the different reflectivity of the reflector surface and light transmission loss in the

12、 optical fiber should also cause measurement error. Therefore, to put forward three probe fiber optic sensor compensation measuring method can eliminate the influence of all kinds of unstable factors in the measuring environment.Figure 1. Reflective intensity modulation type fiber optic sensorB. Thr

13、ee probe compensating optical fiber bundle sensors measurement principleTraditional reflective intensity modulation type fiber optic sensor using a single optical fiber transmitting and receiving the light energy is very weak. Moreover, in the design of wiring, because of the warped shape change the

14、 geometry of the symmetry of thefiber and the relative refractive index of fiber core and cladding, which affect the lateral distribution of the optical fiber mode field, and destroy the total reflection of light waves along the optical fiber transmission conditions, lead to light leaked to the pack

15、et layer and outer layer medium. Therefore, this design is composed of three probe of optical fiber sensor including PCF which use to send and receive light and the additional reference light path, as shown in figure 2.Figure 2. Three probe optical fiber bundle sensorsOrdinary single mode optical fi

16、ber loss theory of improvements can be applied to PCF, gaussian beams transmit along the optical fiber, the relationship between light intensity and bend loss coefficient and length isP(z) P(0)exp( az)(1)a in the formula is bend loss coefficient, andin the formula,2sin 2 c / 2 , Vsinc , W22c12exp( 4

17、RV2 W3)Ae3(2)aWR8 P WV 22 W,is the radius of optical fiber core,R is bend radius,introduce a parameter V222neff/2ns /, when thec1 , under the condition of large mode field, useoptical fiber bending radius R is greater than optical fiber core radius, formula (2) can be written as223a1AeF122 RV(3)86Pn

18、s6nsF (x)x 1/2exp(x)(4)in the formula, ns is refractive index ofSiO2 , Ae is coefficient of electric field in the packet layer, P is power of base membrane,is distance of mesopores in the packet layer. In type (3), V/A increases with air filling ratio (d/A), and F(x) is a monotone decreasing functio

19、n. It turns out that bend loss decreases with the filling ratio, and increase with bending radius. Therefore, we can draw the conclusion: in the case of inevitable bending, we can offset optical fiber bending loss via improving air filling ratios, the bending resistability of PCF will be stronger wi

20、th the increase of optical fiber filling ratio.It is recommended that the light spot of reference light and measurement light on the sample should be consistent, so that reference light can play a role of reference. Therefore, the optical fiber sensing probe adopt the concentric circles structure, t

21、wopaths for launching optical fiber bundle work as inner circle with the uniform distribution random permutation, the outer ring works as the receiving fiber bundle. In the case of enough quantity of measurement optical fiber and reference optical fiber, the spot area produced by exposuring to the o

22、bject with two wavelengths of light. In actual production process measurement and reference fiber bundle are used 4000 each optical fiber glass strand. As a result, it can approximate thought that measuring light and reference light are the same light path, the structure is shown in figure 3. Accord

23、ing to spectrum analysis theory, the light of 635nm wavelength cannot be absorbed by effective light-absorbing substance in the blood, it only related to other light-absorbing factors. So it can be used as reference wavelength. The light in 700nm wavelength is not only associated with light suction

24、material concentration, but also associated with other light-absorbing factors expect this material s influence. Therefore, the light emitted by emitting diode D1 and D2 with the same intensity and two separate wavelengths, 635nm and 700nm, import into optical fiber, respectively after reflection by

25、 the D3, and then get their intensity which can reflects the level of the blood glucose concentration through the spectralcomponents and filter to isolate different wavelengths of light. This kind of optical fiber probe that is arranged closely with the same fiber size and optical path is easy to ma

26、ke ribbon. It can automatically compensate light source intensity and reflectivity andthe influence of environmental factors such as changes on the measurement accuracy.Figure 3. Cross-section of fiber probeII. H AREWARE DESIGNA.System designMonitoring device consists of CPU, three probe fiber bundl

27、e sensor, amplified circuit, LCD, keyboard, type Y splitter, alarmparts, filter, etc. , as shown in figure 4. Its working process is: the program stored in CPU will control the LED driver circuit toproduce a 10 kHz reference wavelength and a measurement wavelength by CPU s IO port.Measuring light an

28、d reference lightirradiate on the blood sample through the three probe optical fiber bundle sensors. And the reflective light import Y type coupler.After passing filter,two beams of light at differentwavelengths willrespectively go into the logarithmicamplificationanddifferential amplification, and

29、then input to the CPU to achieve A/D conversion and data analysis, finally return the result on theLCD.KeyboardLightsource1logarithmicamplificationCPUPCFLightsensorsLEDsource2filterlogarithmicamplificationdifferentialamplificationFigure 4. Structure deviceB. Photoelectric converting and amplifying c

30、ircuit designAccording to theoretical analysis, it s necessary to turn the blood glucose concentration measurement into light intensity ratio measurement. After photoelectric conversion, it turns to measure current ratio. Therefore, to obtain the current ratio needs the logarithmic amplifier and dif

31、ferential amplification. LOG114 amplifier from TI which has two road 2 independent of differential amplifier and a internal reference voltage of 2.5V can meet the needs of the testing. It is dedicated to he detection of the photodiode signal optical fiber cable output. There is no need other circuit

32、s. It also supports to detect 8 orders of magnitude. The dynamic rangeis 100pA 10mA. It has high speed, high accuracy etc. advantages. It is very suitable for light control system, thereby, it can avoid quadratic error brought by the composed of discrete element in the circuit.III. SOFTWARE DESIGNSo

33、ftware structure is mainly composed of main program and interrupt functions and display program modules and program flow is shown in figure 5.StartInitializeEnd ofRAM, LEDsampling?NYKeypress?Stop pulse,Ydata analysisGeneratepulseEnableValueoverflow?interruptionYInterrupt?NAlarmNYRead andDisplaysave

34、dataresultsFigure 5. Program flowIV.EXPERIMENTAL RESULTSWe use this system to collect the blood samples after lunch and dinner, the sampling data are shown in Table 1. After data fitting, we will make comparison between fitting curve and curve measured by blood giucose monitoring system, as shown on Figure 6.Table 1. Sampled data between lunch and dinnerBloodBloodglucoseOutputg