Research On The Specific Detection Of Biomolecules Utilizing S-tapered Structure Based Fiber Interferometer

With the development of social economy and information technology,biomedicine has attracted considerable research interests and has become one of the most important developing fields up to date.Biosensors have been widely used in the areas of disease diagnosis,medical care,drug development and environmental monitoring.The sensitivity,integration and measurement accuracy of biosensors also need to be further improved,and thus advanced bio-sensing technology has become a hot topic in the field of biomedicine.As an efficient detection device that exploits the merits of fiber sensing and biological detection technologies,fiber-optic biosensor provides a new way to achieve label-free biological detection with such desirable advantages as fast response,high safety,low sample consumption and good bio-compatibility.In this dissertation,fiber-optic interferometers based on S-tapered fiber structure have been proposed.The structural characteristics of the fiber sensors and the experimental detection of the specific biomolecules have been investigated.The main work conducted in this dissertation are as follows:1.Modal interference principle of S-tapered fiber has been analyzed theoretically.According to the beam propagation method,a theoretical model for S-tapered fiber has been established,and the relationship between the geometric parameters and the interference spectrum of the S-tapered fiber has been analyzed,which provide a theoretical reference for the fabrication of S-tapered fiber sensors.2.An S-tapered fiber immunosensor functionalized with hydrophobin HGFI has been proposed.The S-tapered fiber is fabricated by a commercial fusion splicer and is packed inside a silica capillary for experimental investigation of immunological detection.Hydrophobin HGFI allows for the formation of a self-assembled film and is the main factor that causes the adsorption of the probe antibody deposited over the fiber surface.The surface-decorated fiber sensor enables immunological recognition of the specific antigen.3.A fiber-optic interferometer based on concatenated S-tapered fibers has been proposed and developed.The modal interference principle has been discussed and the influence of environmental refractive index on spectral intensity has also been theoretically analyzed.The fiber surface is functionalized with Poly-L-lysine(PLL)and single-stranded DNA(ssDNA)probes via ionic absorption.ssDNA molecules with complementary and completely non-complementary base sequences are detected through control experiments.4.A thin-core-fiber-based(TCF-based)dual S-tapered fiber sensor has been proposed and experimentally demonstrated.The principle and characteristics of the fiber interferometer have been discussed and theoretically analyzed.And the optical field distribution has been simulated based on the beam propagation method.The detection of DNA molecules at 1 nM concentration is achieved,and the specificity and repeatability of the fiber sensor are experimentally evaluated.