Micro-optical-fiber Biosensor Based On Interferometer

In recent years,the research of biosensing technology has shown increasingly important significance in applications such as disease diagnosis,environment surveillance,and medicinal development.To broaden the method of biosensor detection,exploring the new mechanism,developing advanced sensor have become the extremely urgent requirement in industry development.With the new information material-fiber proposed,modern biological sensing technology has increased a new way.The optical fiber,with so many advantages such as light weight,small size,high sensitivity,fast response,anti-interference,safety and great biocompatibility,has become one of the most rapidly developing sensing technology in recent years.To achieve the high sensitivity,label free,high specificity and"in vivo" optical fiber biomedical detection technology,and develop the functionalization,integration optical fiber biomedical sensors,has become the hot research topic and future orientation in this area.In this dissertation,a quasi-Mach-Zehnder interferometer(MZI)micro optical fiber biosensor and have been proposed and demonstrated for the carrier element of biosensor,and the fiber surface sensitive biological membrane have the role of recognition element.Owing to the high sensitivity refractive index(RI)and extremely great specificity recognition ability of the biosensor,the analyte biological information can be converted to optical signal which can be demodulated efficiently.Moreover,a Fabry-Perot interferometer(FPI)based on a micro fiber tips has been proposed for compensating the temperature variation in bio-sensing applications.Different from traditional label sensors,the proposed micro fiber interferometer sensor doesn’t need the complex prepare process,measuring the biological sample through the strong evanescent field.These devices,with the advantages of dexterous fabrication,tiny size,high sensitivity,label free,provide a new approach in biomedical sensing.The research mainly contains two parts as follow:(1)A quasi-Mach-Zehnder interferometer micro optical fiber for DNA hybridization detectionDNA complementary sequence detection is monitoring the process of unknown specific target DNA in sample hybridizing with the known DNA sequence.In this part,a quasi-Mach-Zehnder interferometer based micro optical fiber sensor is proposed and fabricated for DNA sequence detection.We splice two short single mode fibers(SMF)on each side of a 20mm long multimode fiber(MMF),and then taper the MMF to the diameter of 10μm by flame.We etch the tapered MMF to remove the fiber cladding by hydrofluoric acid(HF).The fabrication is used in DNA hybridization monitoring.Adsorption method is used to immobilized the Poly-l-lysine and probe DNA molecular,and the quasi-Mach-Zehnder(MZ)interferometer micro optical fiber biological probe can be fabricated successfully.Then,we use the biological probe to detecting the process of DNA specificity hybridization with great repeatability.To certify the result of DNA specificity complementary,we detect the non-complementary target DNA solution.The biological probe with the minimum detectable concentration of 1μM can be used in other biological molecular such as antigen-antibody,histocyte and other field.(2)The research of Fabry-Perot(F-P)interferometer based on micro fiber tipsTo achieve the micro scale biological detection,we propose a Fabry-Perot interferometer(FPI)micro fiber tips sensor,demonstrate temperature and refractive index response of this sensor,and put forward the possibility of detecting huge biological molecular base on the micro fiber tips.Firstly,we fabricate the fiber tips sensor through etching single mode fiber interface and splicing with a short SMF to obtain an air bubble near the fiber core.Then,the end of the SMF is tapped by polarization-maintaining spliced machine in special splicing mode,and the diameter of fiber tips is nearly 2μm.The light reflect on the end-face of fiber tips will couple with the reflected light of the air bubble,forming the Fabry-Perot(F-P)interferometer.We detect the wavelength shift as temperature of micro fiber tips,proving this sensor can be used in micro size with large temperature gradient.We text the refractive index(RI)of the Fabry-Perot(F-P)interferometer micro fiber tips sensor,the response of RI is too slight so that cannot be used in DNA hybridization,however,it can be apply in large biological molecular detection.