Research On PH Detection Technology Of Tilted Fiber Bragg Grating Based On Polymers

pH value is an important index to measure the acidity and alkalinity of solution and a key factor affecting physical,chemical and biological reactions.The detection of pH value is of great significance in the fields of medical treatment,meteorological environmental protection,aquaculture and planting.Especially in medicine,because of the different body fluids have different pH values,pH is commonly used in medicine to express the acidity and alkalinity of body fluids.Traditional pH measurement tools are pH meter,pH test paper,pH indicator,etc.These methods are simple to operate and low cost,but these qualitative measurements have certain limitations.On the other hand,fiber Bragg grating(FBG)is becoming the main detection tool in the field of physical sensing due to its advantages of anti-electromagnetic interference and sensitivity.Therefore,in view of the need of pH detection and the advantages of fiber Bragg grating sensing technology,a novel inclined fiber Bragg grating pH sensor based on polymer coating is proposed and designed.The main work of this paper is briefly introduced as follows:Firstly,the paper introduces the main categories,performance advantages,development history and prospects of fiber optic sensors,and introduces the preparation process,performance advantages,spectral characteristics and application fields of tilted fiber gratings.This paper focuses on the use of its spectral characteristics.Experimental exploration.Secondly,through the investigation of the swelling property of polymer hydrogel and the characteristics of polyethyleneimine/polyacrylic acid(PEI/PAA)multilayer film,the layered self-assembly technique was used to deposit the sensing film on the TFBG substrate.The effect of the sensing film on the refractive index and spectrum of TFBG is made into a sensor to achieve pH detection.In addition,through the investigation of polyaniline,the reversible reaction of its color in different pH environments was applied to coat it on TFBG substrate to explore its effect on the refractive index and spectrum of TFBG,and to make a sensor to detect pH.Through the experimental investigation and data processing analysis of the above two pH sensors,it can be seen that as the pH value increases,the spectral dip angle continuously shifts blue,and the longitudinal width of the spectrum gradually becomes larger.From the experimental data,we can conclude that the detection sensitivity of the pH sensorbased on PEI/PAA multilayer film is 137 pm/pH,and that of the pH sensor based on polyaniline monolayer film is 91 pm/pH.Finally,the glucose biosensor was prepared by coating GOD on the outermost layer of the PEI/PAA multilayer sensing membrane.The biosensor reacted with the glucose solution of different concentration,record the grating spectra for each reaction and compare their changes.It can be seen from the experimental results that when the glucose solution of different concentration is added to the glucose biosensor respectively,the spectral dip angle becomes red-shifted,and with the increase of glucose solution concentration,the red-shift degree of the spectral dip angle increases.This is because the high concentration glucose solution reacts with GOD to a greater extent and changes the pH of the original solution,which is consistent with the detection results of the above-mentioned pH sensors,thus achieving the purpose of detecting sugar molecules using tilted fiber gratings.