Construction Of Thermoresponsive Fibrous Composite Actuator Induced By Alternative Magnetic Field

Thermoresponsive actuators can produce mechanical behavior under the stimulation of external temperature,use water as a medium,and realize the conversion of thermal energy to mechanical energy through heat transfer,showing great application potential in software robots,sensors,and biomedicine.Thermoresponsive smart actuators are composed of thermoresponsive smart materials,generally in the form of a double-layer structure:Thermoresponsive smart materials are used as the active layer,and non-responsive materials are used as the passive layer.When the external environment temperature changes,the active layer material shrinks or expands,while the passive layer remains unchanged.Due to the anisotropy of the two-layer materials,the two-layer structure will be deformed to perform mechanical behavior.However,it is currently facing challenges in its in-depth application.First,this kind of smart actuator mainly exists in the form of polymer film,with compact structure and low response sensitivity.Second,it passively relies on an external heat source to heat the entire system.The heat transfer efficiency is low and uneven,which is not conducive to the accurate expression of the actuation behavior,and the application range is limited.The reason is that this process is too resistant to heat transfer efficiency.In order to overcome this shortcoming,this project is based on the model of magnetism?heat?mechanical energy.With the help of the porous structure of electrospun micro-nano electrospun fibrous mats,the fibers of the ultra-fine electrospun fibrous mats contain magnetocaloric nanoparticles Fe₃O₄,which are heated in situ by a magnetic field.To achieve fast,remote and penetrating control of the actuator.In this paper,thermoresponsive polymer is used as the active layer material,and thermoplastic polyurethane(TPU)is used as the passive layer material.First,the thermoresponsive polymer poly(N-isopropylacrylamide-co-4-acryloxybenzophenone)P(NIPAM-ABP)was synthesized,and it was passed through NMR,GPC,UV-VIS,DSC and FTIR characterizes the polymer,qualitatively analyzes the polymer,and determines the molecular weight of the polymer and its low critical solution temperature LCST.Then the synthetic P(NIPAM-ABP)polymer was used to prepare a spinning solution for electrospinning,which was characterized by SEM and FTIR,and a uniform fiber membrane was obtained.Secondly,in order to better build a stable double-layer composite structure and avoid the occurrence of interface problems,the active layer and the passive layer are composited into actuators in three ways.The first is to use TPU-Fe₃O₄ electrospun fibrous mats and P(NIPAM-ABP)A layer of PCL electrospun fibrous mats is added as the adhesive layer in the middle of the electrospun fibrous mats;the second is to add the photocrosslinking agent ABP to the TPU-Fe₃O₄suspension and then electrospinning,and the double-layer fiber membrane is UV Light cross-linking to make the fibers between the double-layer structure cross-linked and bonded;the third is to use the coating method to coat the TPU-Fe₃O₄ suspension and directly cover the P(NIPAM-ABP)fiber before it is completely dried electrospun fibrous mats.After exploring and studying the interface problems of the above three double-layer structure actuators,it is found that the first two actuators will have interface problems in the water,which affects the stability of the actuator.The actuators made by the third composite method were tested,and none of the actuators showed interface problems.Therefore,the third actuator will be used to study its actuation performance in the follow-up.Finally,the P(NIPAM-ABP)electrospun fibrous mats with randomly arranged fibers and the P(NIPAM-ABP)electrospun fibrous mats with oriented fibers arranged by electrospinning technology were prepared,and they were combined with the TPU-Fe₃O₄ film to prepare a double-layer structure thermoresponsive actuator.Due to the porous structure of the micro-nano fiber membrane,the porosity can reach 70%,which increases the heat transfer rate in the P(NIPAM-ABP)segment.The effect of Fe₃O₄ loading and magnetic field strength on the surface temperature and bending curvature of the actuator was studied.It is found that as the loading of Fe₃O₄ increases,the heating rate and maximum temperature of the actuator will also increase,which in turn affects the bending curvature of the actuator,so that the bending curvature also increases;changing the magnetic field strength,the actuator The surface temperature increases with the increase of the magnetic field strength,and the bending curvature also has the same trend.At the same time,the performance of the magnetic field penetrating medium to manipulate the actuator was studied.The actuator still has stable and efficient actuation performance under the coating of polytetrafluoroethylene(PTFE)film,which demonstrates the air-space control of the actuator sex.Finally,the influence of the fiber arrangement direction on the actuation behavior of the actuator is explored,and it is found that the bending angle of the actuator is the same as the fiber arrangement direction in the actuator.In summary,this subject has successfully prepared a magneto-thermal thermoresponsive actuator,characterized the shape of the actuator,studied the actuation performance of the actuator,and built a heat source to improve the heat transfer efficiency.The actuation time is reduced to a few seconds,and a magneto-thermoresponsive electrospun fibrous mats actuator that is simple to prepare,highly sensitive,controllable in direction,and capable of being controlled in air is obtained.