| Optical fiber sensors have attracted more and more attention in recent years due to their small size,low cost,high sensitivity,anti-electromagnetic interference,and distributed measurement.However,the current researches focus on optical fiber sensors are mainly limited to the sensitivity,ignoring the environmental impacts of the materials used in the sensors manufacturing process.This article has studied and verified various optical fiber sensors based on degradable environmentally friendly polymer materials such as hydroxypropyl methyl cellulose,hydroxyethyl cellulose,carboxymethyl cellulose,and polyvinyl alcohol.The optical fiber sensors used the micro-nano functional film of these degradable materials realized the measurement of temperature,humidity,and glucose concentration.The specific research content are as follows:(1)The classification,development and working principle of optical fiber sensors were explained theoretically.Considering the optical fiber structure,the method that can be used to prepare the optical fiber micro-nano functional film was introduced and the electrospinning technology was also introduced to the preparation of the optical fiber micronano functional film of the optical fiber sensor.(2)The optical fiber sensors with degradable micro-nano functional film manufactured by dip-coating technology were studied.Firstly,degradable hydroxypropyl methyl cellulose was used to dip a layer of 10μm hydroxypropyl methyl cellulose film on the end face of a100μm hollow-core optical fiber to achieve the measurement of environmental humidity.The experimental results indicated that hydroxypropyl methyl cellulose is an excellent humidity sensitive material that can be used for optical fiber humidity sensing.Secondly,a hydroxyethyl cellulose-based optical fiber sensor was designed with the same structure.The sensor was designed by dipping a layer of hydroxyethyl cellulose film with a thickness of10μm on the end face of 150μm hollow-core fiber.The sensitivity of the sensor was224.5pm/%RH and the response time of humidity from 35%RH to 85%RH was only 2.75 s,indicating that hydroxyethyl cellulose is an excellent humidity sensitive material.Then,an optical fiber humidity sensor using carboxymethyl cellulose was designed.The sensor was composed of dipping a layer of carboxymethyl cellulose film on the end face of 100μm hollow-core fiber.The experimental results showed that the optical fiber sensor humidity sensitivity using carboxymethyl cellulose film was 170.55pm/%RH.The sensitivity of the sensor was further improved by adding carbon nanotubes in the carboxymethyl cellulose film.The experimental results showed that the sensor sensitivity was 230.95pm/%RH after the addition of carbon nanotubes,and its humidity sensitivity was increased by 35.41%.Finally,a multi-mode interference optical fiber temperature and humidity sensor using carboxymethyl cellulose was designed.Hydrofluoric acid was used to corrode a 6mm multimode fiber from 125μm diameter to 60μm.And a layer of carboxymethyl cellulose film was dip-coated on the multimode optical fiber sidewall,the humidity sensitivity of the designed sensor was 69.6pm/%RH,and the temperature sensitivity was about 15pm/℃.(3)The electrospinning technology was introduced to the preparation of micro-nano films for optical fiber sensors.The applications of electrospinning in optical fiber sensors were studied.Firstly,the electrospinning process and the influence of various parameters on nanofiber film preparation were explained.Then,an optical fiber temperature and humidity sensor with electrospinning polyvinyl alcohol nanofiber film covered in the tapered area of the optical fiber was designed.The experimental results showed that the sensor humidity sensitivity using polyvinyl alcohol nanofiber film was 0.0369 d B/%RH.After adding carbon nanotubes to the polyvinyl alcohol solution,an optical fiber sensor using polyvinyl alcohol/carbon nanotubes composite nanofiber film was fabricated.The experimental results showed that the sensor sensitivity increased to 0.0484 d B/%RH.Compared with the sensor using polyvinyl alcohol nanofiber film,the humidity sensitivity was increased by about31.16%.In addition,by observing polyvinyl alcohol nanofibers and polyvinyl alcohol/carbon nanotubes composite nanofibers,it was found that after the addition of carbon nanotubes,the cracks of the nanofibers were reduced,and the mechanical strength of the nanofibers were further improved.Finally,a humidity sensor with an electrospinning micro-nano functional thin film on the end surface of a hollow-core fiber was designed.The results showed that the sensor was sensitive to humidity changes,and the humidity sensitivity was 368pm/%RH.(4)The application of electrospinning in glucose optical fiber sensor was introduced.An optical fiber glucose sensor was fabricated using electrospinning as a method of enzyme immobilization.The glucose oxidase was mixed in the polyvinyl alcohol solution,and the mixed solution was electrospinning to produce polyvinyl alcohol nanofibers encapsulating the glucose oxidase.Glutaraldehyde was used to cross-link the polyvinyl alcohol nanofibers so that the modified nanofibers become insoluble in water.Therefore,the D-type optical fiber sensor encapsulated with the glucose oxidase nanofiber film can measure the glucose concentration.Besides,polyvinylpyrrolidone and zinc acetate were mixed and electrospinning.Then the produced nanofibers were annealed to produce nano-zinc oxide,and its applications in glucose sensors and other aspects were prospected. |
PDF Full Text Request