Preparation And Research Of Actuation Strain Actuators For Smart Textiles

Soft actuator is a kind of smart flexible electronics that can convert external stimuli(light,electricity,heat,etc.)into mechanical energy,which breaks the traditional that traditional motors components bear rigid shell.It has wide application prospects in soft robots,micro actuator movers and smart textiles.Dielectric elastomer materials,also known as “artificial muscles”,which generate strain under the action of an external electric field,thus enabling electrical-mechanical energy conversion.The smart flexible actuator devices designed based on dielectric elastomer materials have attracted much attention because of their excellent performance such as low cost,light weight,simple preparation,high electromechanical coupling efficiency(about 90%),and quick response.However,today's dielectric elastomer actuators still face the problem of high drive voltage and low actuated strain.From the drive mechanism of dielectric elastomers,the most effective way to reduce the drive voltage of the driver and to increase the electrically induced strain of the driver is to reduce the elastic modulus of the dielectric elastomer and to increase the dielectric constant.In this study,polyurethane dielectric elastomer was selected as the base material of the actuator,and the effects of reducing the elastic modulus and increasing the dielectric constant were achieved by doping the polyurethane matrix with plasticizers and nano-conductive fillers,respectively.The prepared dielectric elastomer films were characterized in terms of dielectric,mechanical,and electrically induced strain properties: the obtained dielectric elastomer film actuators all have excellent dielectric,mechanical,and electrical drive properties.Finally,the textile-based dielectric elastomer flexible actuators were prepared by combining PTFE fabric with the optimal performance of dielectric elastomer film actuators.The main research contents and results are as follows:Firstly,glycerol-thermoplastic polyurethane dielectric elastomer composites were prepared and their properties were tested and investigated.Small molecules of glycerol were incorporated into the thermoplastic polyurethane matrix as plasticizers to investigate the changes in hydrogen bonding within the dielectric elastomer composites and the effects of glycerol incorporation on the mechanical,dielectric,and actuated strain properties of polyurethane after incorporation of different mass fractions of glycerol into the thermoplastic polyurethane matrix.The addition of glycerol not only reduces the elastic modulus of the dielectric elastomer films,but also improves the dipole polarization and interfacial polarization of the polyurethane composites by reshaping the hydrogen bonding structure of the polyurethane molecular chains,which in turn improves the dielectric constant;finally,the dielectric elastomer materials achieve the effect of improving the actuated strain properties through the dual coupling effect of reducing the elastic modulus and improving the dielectric constant.The results show that the dielectric elastomer composite with 30% glycerol mass fraction can achieve 9.24% actuated strain at 23.30 k V/mm,which is about 1000% higher than the electrostatic strain of pure polyurethane(0.83%)at the same electric field.Then the functionalized graphene-thermoplastic polyurethane dielectric elastomer composites were prepared and their properties were tested and investigated.Graphene,a nano-conductive filler,was selected as a functional filler to be doped into polyurethane matrix for enhancing the dielectric properties and actuated strain properties of dielectric elastomer films.To address the problem of poor dispersion of graphene fillers in polymer substrates,hyperbranched polyacrylamides were grafted on the surface of graphene oxide to improve its dispersion and dielectric properties.In addition,the functionalized graphene conductive fillers were doped into the polyurethane matrix at different ratios to prepare functionalized graphene-polyurethane dielectric elastomer films,and the mechanical,dielectric and actuated strain properties of the films were investigated..The results show that the dielectric elastomer film with 3% mass fraction of added conductive filler can achieve an electrically induced strain value of 16.29% under an electric field of 22.80 k V/mm,which is about 20.36 times higher than that of pure polyurethane(?0.8%)under the same electric field.Finally,the optimal dielectric elastomer film material was selected and laminated with PTFE fabric to prepare a long flexible actuator,and two forms of bending were successfully achieved.