Study On The Spider Silk-based Interferometric Optical Fiber Sensors And Their Characteristics

Currently,biomedical research has put forward new requirements for optical fiber sensors(OFS),OFS should not only have high sensitivity and integration,but also have flexibility and biocompatibility,which means OFS should match biological interface without causing immune rejection of organisms.Spider silk(SS)has biocompatibility,flexibility,light-guiding ability,humidity-sensitive property,and good mechanical property,and can be integrated with optic devices to realize optical sensing.Therefore,SS has research value.However,the optical coupling method for the SS biophotonic waveguide used in sensing has low integration and poor vibration resistance,and the SS-based optic device cannot work in the high humidity range because of the humidity threshold limitation caused by SS supercontraction.Photolithography technology can be used to make highly integrated SS-based optic devices,but its fabrication process is complex and expensive,and the SS-based optic device made by using photolithography technology has not yet been used for optical sensing.Overall,the research on SS in the field of optical sensing is still in its infancy.To promote the development and application of integrated SS-based optical sensing devices,the following issues need to be addressed: how to make the SS-based device has a wide humidity working range;how to achieve cheap and stable integration of spider silk and other optical devices.This thesis takes SS-based interferometric OFS as the research object,develops cheap and stable SS-based interferometric sensing devices,and improves the integration of the SS-based optic device.The completed works are listed as follows:First,based on the theoretical analysis of constructing the highly sensitive Fabry-Perot(FP)interferometric OFS,the supercontraction of spider dragline silk(SDS)is used in the fabrication of the highly-sensitive F-P interferometric humidity sensor,whose average sensitivity is 11.89 nm/%RH.The sensor is capable of respiratory monitoring,and it can detect fast and slow respiration in real time with a monitoring distance up to 30 cm.The sensor has high sensitivity by using the SS as a driving component,and the SS is not involved in the optical interference process.The whole structure of the sensor is a bit big,its width reaches 26 mm,so that the integration of the sensor is low.Next,based on the water absorption and swelling property of spider egg-sac silk,an SSfiber integrated F-P humidity sensor fabrication method is proposed,and the SS participates in the reflection process of light beam.The sensor’s sensitivity is only-0.29 nm/%RH,but the whole diameter of sensor is reduced to 100 μm,the integration is greatly improved.This integrated SS-based OFS has compact structure,portability,and low-temperature cross-talking.Then,based on the structure-property of SDS,that is,the consistent orientation of the crystals in SDS will move to the disordered state after the water absorption,SS is used as a humidity-sensitive optical waveguide in the construction of an integrated multimode interference optical sensor based the winding method.This new kind of integration method makes the SS-based sensor avoid the limitation of supercontraction humidity threshold,and the humidity sensing range is 30%RH～89%RH.The whole diameter of the sensor is reduced to about 13 μm,and the sensor’s integration is further improved.The proposed sensor has low cost and high integration,and the average sensitivity is improved to 0.53 nm/%RH,which provides a new method for the fabrication of the SS-fiber integrated optic devices.Finally,based on the multimode optical waveguide property of SDS,the evanescent field optical coupling method is used to realize the cheap and stable SS light coupling structure.Spider silk is used as a micron optical waveguide which has light transmission and sensing functions to construct the SS-based optical mode interferometer.A two-step packaging method is proposed and used to embed the interferometer in the flexible thermosensitive material to avoid the influence of humidity variety on SS.The diameter of the SS-based mode interferometer’s core structure is less than 8 μm,the interferometer has high integration and linear response to temperature,and the sensitivity is-1.15 nm/℃.The SS-based interferometer has compact structure,stable optical coupling,portability,and resistance to humidity variety,which provides a new way to fabricate integrated SS-based optic devices.Overall,this thesis proposes kinds of methods for integrating SS with optical fibers,and develops interferometric optical sensing devices by using SS.The proposed SS-based devices are not limited by the humidity threshold of SS supercontraction.These studies provide effective methods for the further application of SS in the field of optical sensing.