Research Of Properties And Driving Characteristics Of Hydrogel/Carbon Nanotube Composites For Fiber Artificial Muscle

In recent years,fibrous artificial muscles have made exciting progress which attract much attention due to their excellent driving characteristics and broad application.Hydrogel materials have unique soft and wet properties and good biocompatibility.More and more artificial muscles of hydrogel materials have been developed,but artificial muscles based on hydrogel fibers have not been reported.Based on the relationship between the water content inside the hydrogel fiber and the volume of fiber response characteristics,a double-network hydrogel fiber composed of silica nanoparticles and polyacrylic acid was designed in this paper.A hydrogel fiber was wrapped up with highly anisotropic carbon nanotube(CNT)film to prepare composites fiber with core-shell structure.The composites fibers were used to design a torsional double-helix artificial muscle and a tensile coiled artificial muscle.Driving properties of artificial muscles were studied.The main research contents of this article are as follows:1.The sol-gel method was used to prepare silica nanoparticle dispersions(VSNPs),and acrylic acid was graft polymerized in situ to obtain physically cross-linked double-network hydrogel fibers.SEM,FTIR,TGA,gravimetric method and Instron mechanical tester were used to discuss the morphology,structures and properties of hydrogels and hydrogel fibers.The experiments found that the double-network hydrogel and double-network hydrogel fibers have strong water absorption capacity.The massive hydrogel can absorb 1.57 times of relative its own mass in 30 minutes.The hydrogel fiber can absorb 51.8 % of relative its own mass and the double helix hydrogel fiber can produce 50 % tensile deformation relative to its length in 100 % RH.2.Hydrogel fibers were wrapped up with anisotropic CNT film to prepare the core-shell structure hydrogel/CNT composites fibers.Torque-balanced structures that are obtained by folding a twisted fiber onto itself(by bending at fiber midpoint).Double helix artificial muscles can be torsional and axially tensile under water fog.Changing the wrapping angle of CNT wrap up hydrogel fibers can regulate the driving performance of double helix artificial muscles: When the hydrogel/CNT wrapping angle is 0 °,double-helix artificial muscle with 11 % contraction in the axial direction provide high-speed torsion with a torsional angle of 1455 °/mm and a maximum rotation speed of 3178 rpm;when the hydrogel/CNT wrapping angle is 85 °,a double-helix artificial muscle with a tensile stroke up to 54.8 % in the axial direction is obtained,but torsional stroke is reduced by 501.3 °/mm and the maximum rotation speed is 720 rpm.In addition,the twist density,diameter of the composites fiber,and the water moisture concentration are also factors that influence the driving performance of the double helix artificial muscle.We tried to weave composite fibers in four ways to obtain double-helix artificial muscles with different weaving structures.The experiments found that the B and D weaving methods have better driving performance.3.Tensile hydrogel/CNT composites fiber muscles were obtained by coiling a twisted composites fibera mandrel and then thermally setting.When the twisting direction of the composites fiber is the same as the coiled direction,an homochirality artificial muscle(zz or ss)contracted in the wet air is obtained;when the twisting direction of the composites fiber is opposite to the coiled direction on the thin rod a heterochiral artificial muscle(zs or sz)elongated in the wet air is obtained.The driving performance can be adjusted by changing the twist density,spring index and coil gap of the coiled artificial muscle.A-95.7 % contraction deformation of homochirality artificial muscle was obtained at no load under the driving conditions of 80 % RH,the twisted density of homochirality artificial muscle is 6000 turns/m,the spring index is 15,the coil gap is 1 mm.During this process,homochirality artificial muscle showed an average response rate of 13.67 %/s;2600 % elongation deformation of heterochiral artificial muscle was obtained at no load under the driving conditions of 80 % RH,the twisting density is 6000 turns/m,the spring index is 7.5,the coil gap and the fiber diameter are similar.The tensile performance of two kinds of chirality artificial muscles are driven 50 times under the condition of 20?60 % RH has no change,and they have good cycle drive performance.