Research On Micro/Nano Optical Fiber Sensor Based On PDMS Functionalization

The development of science and technology has driven the continuous progress of optical fiber technology,and the research of optical fiber sensor has attracted more and more attention.Compared with other types of sensors,optical fiber sensors have the advantages of high sensitivity,small volume and high integration.They have a wide application prospect in the fields of cutting-edge science and technology,military aerospace,biological detection and so on.Based on the previous research background,this paper has prepared high-performance optical fiber sensors based on micro/nano fiber,and carried out the research on biomineralization monitoring sensors based on Tapered Two Mode Fiber（Tapered Two Mode Fiber,TTMF）,optical fiber magnetic field sensor based on magnetic polydimethylsiloxane microspheres（Magnetorheological Polydimethylsiloxane,M-PDMS）and wearable shape sensors based on PDMS integrated Tapered Two Mode Fiber.The main research contents are as follows:（1）Biomineralization monitoring sensor based on t Tapered Two Mode Fiber.With the help of the strong evanescent field effect of TTMF,the process of“water to gold”of D.acidovorans bacteria was monitored in real time.A single mode fiber-two mode fiber-single mode fiber（single mode-two mode-single mode fiber,STS）interferometer structure is designed.Based on the mode interference effect between HE₁₁ and HE₁₂ modes,Through the change of interference spectrum（wavelength and intensity）,the real-time monitoring of D.acidovorans bacterial mineralization process is realized.In order to enhance the binding efficiency between D.acidovorans bacteria and bare ttmf,the surface of ttmf was functionalized.TTMF was pretreated with silane coupling agent（3-aminopropyl）triethoxysilane（（3-aminopropyl）triethoxysilane,APTES）,and then D.acidovorans bacteria were transferred to the outer surface of TTMF.In order to ensure the stability of the structure test,a special PDMS microfluidic sample tank is designed,and the STS structure is integrated in the tank to improve the accuracy of the test results.When D.acidovorans bacteria interact with water-soluble gold ions in the test environment,the evanescent potential field on the surface of the optical fiber is changed,resulting in the change of STS output transmission spectrum.The detection of biomineralization is realized by tracking the wavelength drift at the dip point of the transmission spectrum.The experimental results show that when the bacterial concentration of D.acidovorans is 30μm and 100μm Au³⁺,the corresponding spectral drift is～8.4 nm and 4.8 nm,respectively.（2）Optical fiber magnetic field sensing based on magnetic polydimethylsiloxane microspheres.M-PDMS microspheres are prepared by self-assembly method.At the same time,micro/nano fiber is combined to couple the transmission light field,excite echo wall resonance mode（Whispering Gallery Mode,WGM）,change the environmental magnetic field intensity,monitor the changes of WGM spectrum in real time,and realize magnetic field sensing.Preparation of M-PDMS microspheres,Mn₃O₄ nanocrystals with uniform size are mixed into PDMS matrix,micro/nano fibers are combined with PDMS matrix,and microspheres chains are obtained in the cone waist region to form PDMS micro resonators.The experimental results show that a high Q-value WGM spectrum is formed near 1310 nm,Q=10⁴.Due to the magnetostrictive effect,the change of the external magnetic field will cause the mechanical deformation of the PDMS micro resonator and the shift of the resonance wavelength,so as to realize the highly sensitive detection of the micro magnetic field.（3）wearable shape sensors based on PDMS integrated Tapered Two Mode Fiber.Using the strong evanescent field characteristics of TTMF structure and the large thermooptical coefficient of PDMS flexible material,PDMS is combined with TTMF to achieve highly sensitive responses to temperature,tension and bending.The sensitivity is 1.4 nm/℃,20.6 nm/mm and 1.34 nm/m^-1respectively.The sensor can be used to monitor human movement processes such as human respiration,arm movement and body temperature.