| Magneto-sensitive elastomer(MSE)is a class of intelligent elastomer materials embedded with magnetic particles in a polymer matrix,which exhibits rapid and reversible mechanical behavior under the action of an external magnetic field.Therefore,MSEs are widely used in vibration control,soft robots,bionic actuators and flexible electronics.According to the distribution of magnetic particles in the matrix,MSEs are divided into isotropic elastomers and anisotropic elastomers.Compared with isotropic MSEs,anisotropic MSEs have more pronounced mechanical-magnetic coupling behavior.Currently,the mechanical-magnetic response of anisotropic MSEs containing different types of magnetic particles has been investigated.It is found that the anisotropic MSEs doped with superparamagnetic particles are difficult to be applied in practical engineering due to the problems of easy agglomeration and weak magnetism.Although hard magnetic particles-enhanced anisotropic MSEs have unique magnetorheological properties and excellent magnetic field-induced deformation ability,the magnetic attraction between their internal particles causes non-uniform magnetic actuation.Therefore,most of the current researches focus on the magnetic field-induced behavior of soft magnetic particles-enhanced anisotropic MSEs.However,there is still a lack of in-depth understanding of the relationship between macroscopic properties and microstructure,the mechanism of anisotropic behavior,and the application in smart actuating system.Therefore,on the basis of traditional preparation methods,this paper proposed a new type of soft magnetic particle-doped anisotropic MSE by regulating the orientation of the magnetic particle chain,external shape and material composition.The mechanical-magnetic coupling behavior of anisotropic MSE was systematically studied by experimental test characterization,theoretical and numerical analysis.The basic research on its application in flexible grippers,soft robots,intelligent actuators,circuit switches and soft manipulators was also conducted.The main research contents are as follows:1.Study on mechanical-magnetic coupling properties of anisotropic MSE.Using carbonyl iron particles(CIPs)and polydimethylsiloxane(PDMS)as the main components,anisotropic MSEs with different particle chain orientations were prepared by regulating magnetic field.The influence of particle chain distribution characteristics on the initial modulus,magnetic field-induced modulus,magnetorheological effect and magnetic field-induced force of the samples were explored through quasi-static shear,oscillatory shear and shear-free experiments.The experimental results showed that when the orientation angle of the particle chain changed by 15°,the magnetorheological effect of the anisotropic MSE increased by 127%.The orientation of particle chain had a certain effect on both the magnetic field-induced torque and the magnetic fieldinduced normal force of the anisotropic MSE.The experimental results were analyzed using the modified magnetic dipole theory.Based on the above experiments,the threedimensional origami deformation behavior of anisotropic MSE composite structures under the action of magnetic field was further explored,which provided important reference value for the application of anisotropic MSE in the field of controllable programming deformation of complex flexible structures.2.Study on the magnetic field-induced deformation properties of anisotropic MSE film.A novel magnetically sensitive elastomer film(MSEF)with out-of-plane particle chains has been developed by a two-step method of spin coating and prestructuring.The influence of particle chain orientation,carbonyl iron particle content,sample thickness and magnetic flux density on the magnetic field-induced deformation was experimentally studied.The results showed that under a uniform magnetic field of 87 mT,the off-plane bending angle of MSEF-30° could reach 70.78°.The MSEF-20°could lift heavy objects up to 66.4 times its own weight.The magnetic field-induced deformation of the films was calculated by numerical analysis method,which well explained the experimental phenomenon.Based on the magnetic dipole theory and the deformation equilibrium relationship of thin film,the deformation behavior of the films under uniform or non-uniform magnetic field was analyzed,and the deformation mechanism was clarified.The bionic flexible actuators with double-bending configuration and self-sensing ability were designed based on the MSEFs.Both actuators could achieve the expected goals,indicating that the anisotropic MSEFs have great potential in the field of soft robots and intelligent actuators.3.Study on magnetic field-induced deformation properties of shape-material bianisotropic MSE.Inspired by the shape and stress response of mimosa,a novel shape-material bianisotropic MSE doped with soft magnetic particles was developed.The deformation properties of bianisotropic MSEs were investigated through experiments and simulations.The results showed that under magnetic fields with different directions,the bianisotropic MSEs exhibited shrinkage/elongation deformation configurations,respectively.The deformation of diamond-shaped and regular hexagonal samples based on bianisotropic MSE was 2.4 and 1.7 times that of single anisotropic samples,respectively.On the basis of experiments,the energy equation of beam deformation was established,and the magnetic field-induced deformation of MSE was analyzed.The influence mechanism of anisotropic characteristics on the magnetic field-induced deformation behavior was clarified.Based on the bianisotropic MSE,its applications in magnetic flexible catcher,flexible circuit switch and intelligent control system were discussed,indicating its potential application in flexible electronics and other fields in the future.4.Study on deformation behavior of photo-thermal-magnetic multifield driven anisotropic MSE.A multiple stimuli responsive elastomer composite was developed by introducing temperature-and infrared light-sensitive polydopaminecoated liquid crystal elastomer(PDA@LCE)onto anisotropic MSE.Through experimental test analysis,it was found that the elastomer composite had the ability of controllable deformation in response to light-heat-magnetic multi-field.Among them,the photothermal deformation of PDA@LCE was related to the ambient temperature,irradiation intensity and irradiation time.The magnetic field-induced deformation amplitude of MSE could be adjusted by particle chain orientation and magnetic flux density.Based on the photo/thermal shrinkage of liquid crystal elastomers and the magnetic field-induced bending of MSEs,the elastomer composites showed complex three-dimensional deformation configurations(contraction-bending and bidirectional bending)under the control of magnetic and thermal fields.By changing the distribution of liquid crystal elastomers and the orientation of liquid crystal molecules,the elastomer composite would exhibit the light/thermal deformation of rolling,curling and bending.Taking advantage of the characteristics of photosensitive local regulation and thermal/magnetic global regulation,the elastomer composite could achieve multi-mode deformation and programmable actuation.Based on this,the flower-shaped actuator and hand-shaped actuator were designed.The test results proves the potential application of the elastomer composite in the field of soft manipulators. |
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