The Construction and Response Behaviors to External Fields of Hyaluronic Acid/carbon Nanotube Multifunctional Fibers

Author:Zheng Zuo

Supervisor:zhang dong xing

Database:Doctor

Degree Year:2019

Download:56

Pages:150

Size:7965K

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Carbon nanotube(CNT)fiber is a new type of macro CNTs material after carbon nanotube powder and films.The unique assembly structure of CNT fibers endows abundant interfacial structure in fibers and excellent mechanical,electrical,magnetic,optical and thermal multi-field coupling properties,therefore,it becomes an attractive material for new nanomaterial devices.However,the excellent properties of carbon nanotubes is still difficult to be fully-embodies in macroscopic scale due to immaturity and instability of the fabrication technology and defects in fibers.With the development of nanotechnology,the miniaturization of functional devices makes the fabrication of carbon nanotube fibers more and more urgent.Based on the dispersion effect and matrix combining effect of hyaluronic acid(HA),multifunction HA/SWCNT fibers with uniform shape,controllable length,excellent mechanical,conductivity and electrochemical external field response behaviors were assembled with single-walled carbon nanotubes(SWCNT)as raw materials and HA)as biosurfactant.And the mechanism of electrochemical response characteristic and electrochemical coupling actuation behavior of HA/SWCNT fibers were revealed.Two modification methods of HA/SWCNT fibers were designed based on the external field response characteristics,which effectively improved the mechanical properties,mechanical stability,electrochemical response characteristics and electrochemical coupling actuation behavior of fibers.Then,two nanodevices were further developed using these two modified HA/SWCNT fiber materials.A new wet spinning system of CNT fiber was innovatively designed by studying.the dispersion properties and fiber forming mechanism.The spinning parameters were optimized by studying the dispersion properties of spinning stock,electrical and mechanical properties of fibers.This work realized the macroscopic preparation of carbon nanotube materials and stable preparation of HA/SWCNT composite fiber.The morphology,structure and composition of HA/SWCNT composite fibers were investigated,and the oriented distribution of SWCNTs in fibers was revealed.The influence of different concentrations of SWCNTs in spinning solution on response behaviors to external fields of HA/SWCNT fiber was also performed.The results show that HA acts as bio-surfactant and ion-conducting binder to improve the dispersion of SWCNTs resulting in enhanced electrical and mechanical properties of SWCNT fiber.The highest conductivity of the prepared HA/SWCNT fibers was 109.89±14.55 S/cm,and the tensile strength and Young’s modulus was186.37±15.19 MPa and 18.54±1.12 GPa,respectively.The maximum specific capacitance obtained by cyclic voltammetry could reach 59.08±4.74 mF/cm2.Moreover,HA/SWCNT fibers exhibit electrochemical actuation when electrically charged in an electrolyte with the mechanisms of quantum mechanics effect and double layer electrostatic effect.When an electrochemical charge was injected onto the surface of the HA/SWCNT fibers,the layer of ion water clusters in the double layer at the surface of the HA/SWCNT fibers became thicker,charge-accumulation layer at the HA–SWCNTs–electrolyte interface from the electrolyte ions was enhanced.The presence of HA facilitated the immersion of electrolyte into fibers and provided ion migration channels to achieve rapid ion migration.Therefore,this was benefit to higher capacitance and actuation strains.HA/SWCNT/HMDA composite fibers were prepared by chemical crosslinking modification with HMDA as crosslinking agent and HA/SWCNT as raw material.The study showed that HA was crosslinked to prevent the degradation of itself and the leaking of SWCNTs from fibers.Crosslinking of HA hydrogel significantly enhanced mechanical properties,stability of electrical conductivity,resistance to biodegradation,capacitance and creep of HA/SWCNT fibers.In addition,the obtained crosslinked HA/SWCNT/HMDA fibers showed excellent capacitance and actuation behavior under mechanical loading with the low potential of±1 V in a biological environment.Furthermore,the microfiber actuator based on HA/SWCNT/HMDA fibers exhibited good flexibility,excellent mechanical performance and good biocompatibility,the early inflammatory response can be resolved in less than three weeks after implantation of fibers in subcutaneous tissue of mice.A novel core-shell flexible fiber-shaped electrode material was fabricated using HA,CNTs,and polyaniline(PANI)by a combination of wet spinning and electrochemical polymerization.The morphology,structures,flexibility and electrochemical properties of HA/SWCNT/PANI fibers were studied.The results showed that theπ-πbonds between SWCNTs and benzene ring,and the hydrogen bonds between PANI and HA/SWCNT fibers in the core-shell structure enhanced the stability of PANI deposited on the HA/SWCNT fiber electrode.The obtained core-shell HA/SWCNT/PANI fibers showed about six fold increasing in specific capacitance compared with HA/SWCNT fibers.88.27%capacitance of HA/SWCNT/PANI fibers was retained after 3000 cycles’CV test at the scan rate of100 mV/s.In addition,the core-shell HA/SWCNT/PANI fiber displayed excellent flexibility and electrochemical cycling stability under bending and twisting.The HA/SWCNT/PANI fibers showed an approximately 14%decrease in capacitance over100 bending cycles and PANI structure was unbroken after twisting.An asymmetric fiber-shaped supercapacitor was designed and prepared by using HA/SWCNT/PANI fiber as the positive electrode,CMC/Buckypaper film as the negative electrode and H2SO4/PVA gel as the electrolyte.The working voltage window of the supercapacitor enlarged from 1 V to 2 V,energy and power densities could reach 1.09 mW/cm2 and 12.55μwh/cm2,respectively.