| Human nerve and muscle cells are fibrous morphology,and they exhibit excellent signal transmission,motion transmission,defense and other physiological functions.Inspired by such natural fiber structure,the construction of a new type of intelligent fiber material with bionic structure and function is one of current research hotspots.Hydrogel fiber is a kind of excellent biomimetic materials,which possesses tissue like characteristics of hydrogels such as high-water content,soft and elastic properties,as well as structural advantages of fibers such as high aspect ratio and anisotropy.Therefore,they have a wide application prospect in tissue engineering,biomedicine,flexible sensing and intelligent actuators.However,most hydrogel fibers still display low mechanical strength and uncontrollable swelling,which is difficult to match the mechanical and long-term service of natural human tissue in the variable stress field and complex temperature/humidity environment.Therefore,this dissertation is based on the bioinspired construction of nanocomposite hydrogel fiber,with clay nanoplatelets as physical cross-linkers,poly(ethylene glycol)methyl ether methacrylate and acrylamide as co-monomer.Such bioinspired nanocomposite hydrogel fibers were constructed by spider silk like“dynamic polymerization drawing”process,and were modified by in-situ oxidation polymerization and hierarchical twisting.Such fibers possessed high mechanical properties,light propagation properties,conductivity and multi-environment stability,displaying further applications in fields of flexible strain sensing,damping and intelligent actuators.The specific research contents and main results are as follows:1.Design and construction of nanocomposite gel fiber as light guide,as well as investigation of condensed structure evolution and strain sensing capability of such gel fibers.Taking advantages of clay based nanocomposite hydrogel precursor polymerization process,the glycerol-introduced nanocomposite hydrogel fibers(GN-Fibers)were prepared by“dynamic polymerization drawing”process inspired from spider silk spinning.Among them,Oligo(ethylene glycol)methacrylate(OEGMA)and acrylamide(AM)were selected as comonomer.The results showed that the drawing process during the fabrication endowed GN-Fibers with aligned polymer-clay microdomains,resulting in enhanced tensile strength(9.76 MPa),toughness(10.37 MJ·m-3)and optical propagation properties(0.26 dB·cm-1).Moreover,due to the strong hydrogen-bonding between glycerol and water,such GN-Fibers showed good antifreezing properties(-20°C)and long-term stability(>5 days)at room temperature or high temperature.In addition,stable,reliable,and repeatable GN-Fiber based strain sensors were assembled for quantitative detection of large strains(100%),subtle human motions(finger bending)and pressure(0.02-25 k Pa)in real time through the strain-optical signal attenuation mechanism.Such tough and flexible GN-Fibers displayed a broad application prospect in the fields of wearable sensing or artificial intelligence.2.Design and construction of conductive gel fiber with heterogeneous network structure,as well as investigation of strain sensing and stability of liquid environment of such gel fibers.On the basis of the high strength nanocomposite hydrogel fibers,the hybrid hydrogel fibers with heterogeneous networks,conductivity,and stable strain sensing performance were prepared by constructing polyaniline conductive network inside the nanocomposite hydrogel matrix.The results showed that the hybrid hydrogel fiber has excellent tensile strength(7.21 MPa)and fracture toughness(17.2 MJ·m-3)due to the abundant non-covalent intermolecular interactions and uniform distribution of flexible and rigid polymer chains after introduction of polyaniline networks.Moreover,the hybrid gel fibers had dual-channel of ion and electron,which made it have excellent conductivity(87.99 S·m-1),extremely low electro-mechanical signal delay(4.5%),strain sensing sensitivity(GF=2.85?17.89),and accurate human motion sensing performance.In addition,the hybrid gel fibers were immune to interference from versatile environments,contributing to stable and sensitive monitoring of human motions under air or liquid conditions.Such hybrid gel fibers would function well as wearable and implantable sensors in the fields of health monitoring and human-machine interactions.3.Design and construction of bioinspired nanocomposite gel fiber with hierarchical helical structure,as well as investigation of its mechanical properties and applications.On the basis of the“dynamic polymerization drawing”process,N,N-dimethyl acrylamide(DMAA)monomer with hygroscopicity and elasticity was introduced into the precursor to fabricate high strength and hygroscopicity nanocomposite hydrogel fibers.Further inspired by widely existed hierarchical helical structure in nature(spider silk,morning glories,etc.),hierarchical helical nanocomposite gel fiber bundles with high toughness,good damping capacity,and response properties were constructed by wet twisting and drying processes.The results showed that with the increase of twist degree from 0 TPM(twist per meter)to 450 TPM,the mechanical strength of single gel fiber increased from 19.46 MPa to 23.14 MPa,but the elongation decreased from 99.27%to47.25%.The optimal twist of double-stranded gel fiber was 250 TPM,which could achieve the maximum tensile strength of 19.12 MPa and the fracture toughness of 13.22 MJ·m-3.The toughness of hierarchical helical nanocomposite gel fibers is greatly improved from 7.37 MJ·m-3 of single gel fiber to 21.67 MJ·m-3 of H-8(+)and 18.96 MJ·m-3 of H-8(-).In addition,the H-8(+)gel fiber performed excellent kinetic energy dissipation,damping capacity,and good hygroscopic actuating properties(output power density is 5.6×10-8 W·kg-1).Therefore,the hierarchical helical nanocomposite gel fibers showed potential applications in diverse fields,such as damping,elastic shape memory and water vapor actuators. |
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