Biosensors Based On Exposed-core Microstructured Fiber

With the progress of modern society and science,people are constantly extracting information about the biological composition.In order to meet the needs of people to explore the mysteries of life,it is necessary to develop biosensors with new sensing mechanisms.The microstructured optical fiber(MOF),which serves as a sensing platform,can control the refractive index difference between the core and cladding through the flexible design of the geometric structure.Compared with the traditional biochemical detection methods,the biosensors based on microstructured optical fiber have been highly valued by researchers for their advantages of fast response,simple measurement steps,good stability and high specificity.The sensing principles of the widely used optical fiber biosensors were fiber mode interference,Fabry-Perot interference,and Mach-Zehnder interference.On the basis of making an exposed-core microstructured fiber,the fabrication and application of the above interference sensors have been studied.The main content was divided into the following three parts:(1)Theoretical analysis of the interferometric sensor based on the exposed-core microstructured fiber.In order to realize on-line and real-time detection of optical fiber biosensors,we designed an exposed-core microstructured fiber with flexible structure,low transmission loss and strong evanescent field.By inserting an exposed-core microstructured fiber into two sections of single-mode fiber,a Mach-Zehnder interferometric sensor based on free space propagation-core mode has been proposed.The optical software(Rsoft)was used to simulate various factors that can affect the sensing element,the relationship between the refractive index of the external environment and the wavelength of the transmission spectrum was theoretically analyzed.Finally,the relationship between the thickness of the biomolecule layer,the refractive index and the transmission spectrum was theoretically studied.(2)Biosensors based on exposed-core microstructured fiber were applied to the salinity detection.The fabrication of biosensor based on exposed-core microstructured fiber was described,and its refractive index sensitivity,temperature,real-time detection and other properties were studied.The experimental results show that the proposed sensor has a salinity measurement range from 0 ‰ to 40 ‰ and a salinity sensitivity of around-2.29 nm/‰,corresponding to a refractive index sensitivity of-13103.16 nm/RIU.The measurement error caused by the temperature is only 0.02 ‰/°C,which can be neglected in practical applications.This kind of sensor also presents a Fabry-Perot interference phenomenon besides the Mach-Zehnder interferometer,which shows a flexible sensing structure.The proposed sensor interacts directly with the surrounding solution,which has advantages of high sensitivity and quick response to kinetic changes of the analyte.(3)The ring laser sensor based on No-core optical fiber was used to detect the gene fragment of deafness.In order to achieve hybridization detection of label-free DNA biomolecules,the sensor performances(such as refractive index,resolution,etc.)were tested.The deaf genes were fixed on the surface of the optical fiber after functionalized treatment,and used to detect DNA solutions of different concentrations.It comes out that this sensor has the ability to recognize deaf gene solutions with concentrations above 1?M.For the detection of DNA solutions with a concentration below 1?M,the sensitivity and spectral resolution of optical fiber laser sensor need to be further optimized.Under the premise of optimizing the sensitivity,resolution and stability,the fiber laser sensor is expected to become an analysis tool to achieve high sensitivity,low concentration and real-time detection of target sequences.