Optical Fiber Integrated Microfluidics Sensing Key Technology

With the increasing maturity of fiber optical technology,microfluidic optical devices provide more opportunities and wider applications for the interaction and detection between light and materials,such as microfluidic chip,biochip,lab-on-chip.Compared with traditional microfluidic devices,optofluidic devices using optical fiber as the in-out waveguide have the advantages of simple construction,low cost and high sensitivity and have wide applications in chemical,environmentology,biosynthesis,drug delivery and other fields.However,the coupling efficiency between optical fiber and chip is low and the limited contact area between the waveguide and the sample confines the application of the optofluidic chip.In this paper we used special microstructure optical fiber to construct the experimental structure for microfluidic detection inside the microstructure fiber.The optical waveguide can be combined with material detection to produce highly sensitive sensors based on different microstructure optical fibers by means of structural design or micro-processing.Different kinds of the fiber optical microfluidic sensors based on principles of phase modulation and intensity modulation are fabricated by different microstructure fibers,which solves the low coupling efficiency and low integration of optical microfluidic system.This thesis mainly includes the following contents:1.A variety of hollow microstructure optical fibers with one or multi air holes are designed and fabricated.The proposed fibers include twin-core fiber with an eccentric hole,twin-core fiber with lune core and eccentric hole,twin-hole twin-core fiber,twin-hole twin-core fiber with a rectangular core,hollow fiber with suspended core and hollow twin-core fiber with ring cladding.Through theoretical simulation,the relationship between the spacing of two cores and the coupling of the evanescent field was calculated,which determines the final size of microstructure optical fiber.The optical fibers were characterized,including:the geometry size and the refractive index profiles.Optical devices and potential applications are proposed on the basis of different structural features of the fibers.2.Various micro-processing technologies are researched in detail such as fiber polishing technology including fiber side polishing technology and fiber end polishing technology,hole drilling technology including fiber surface CO₂ laser etching technology,fiber end grinding drilling technology,fiber melt-inflating drilling technology,fiber surface fixed point strong acid etch technology.Providing a convenient method for high throughput analysis and detection such as chemical,biological and medical field.3.Fulfilling from designing to characterizing and improving the fiber optical integrated optofluidic interferometers based on microstructure fiber.?1?A Michelson interferometer sensor based on side polishing symmetrical twin-core fiber is designed and fabricated.The sensitivities of the sensor from refractive index of 1.36 to that of 1.41 are measured.The sensitivity can reach to 74.29nm/RIU when the fiber core is polished 1?m.This sensor demonstrates the practicable of the twin-core fiber integrated interferometer.?2?A kind of microfluidic interference sensor based on an eccentric hole twin-core fiber is designed.On the premise of ensuring the efficient coupling of the interferometric optical path,the microfluidic structure is obtained by conducting sample injection analysis on the fiber surface?3?On this basis,The optical fiber structure was improved and the annular cladding hollow twin-core Michelson interference sensor was designed,which realized the high-sensitivity interference detection of micro-flow,and its sensitivity could reach 2508nm/RIU that can be used for the analysis of.optofluidic sample.The interferometric microfluidic on-line detection model was provided,in which the air hole running through the whole device provides a relatively sealed and stable circumstance.The core suspended on the airhole greatly increases the contact area between the core and the sample liquid,and the concentration of the sample can obviously influence the optical path difference between reference arm and interference arm which greatly improves the sensitivity.4.Fulfilling the design and the fabrication of an optofluidic chemical reactor based on hollow optical fiber with a suspended core on it.The chemiluminescence reaction was realized in the fiber with vitamin C as the sample.The luminescence of luminol-hydroperoxide chemiluminescence system inhibits by Vitamin C.The light intensity output in the fiber decreases as the concentration of vitamin C microfluidics increases In addition,the fluorescence quenching process is realized by nitrite as the determinand in the fiber.With the increase of nitrite ion concentration,the fluorescence quenching rate of the rhodamine 6G increases gradually.The relation between fluorescence intensity and the concentration of the sample is established.The above experiments have realized the rapid mass transfer process of multi-component micro-fluids in the fiber,and completed the efficient optical signal coupling collection and sample trace analysis,which plays an important role in improving the integration of optical fluidic chemical reaction devices and the detection of microbiological and chemical samples.