Research On The Design And Theory Of Dielectric Elastomer Bionic Structure

Inspired by nature,soft materials and bio-inspired structures based on soft materials have attracted more and more researchers.Most attention has been paid to a kind of smart soft active materials that can deform under specific external stimuli.Dielectric elastomer(DE)is a typical electroactive polymer(EAP),which can deform under the action of the electric field.It has the advantages of large deformation,fast response,high energy density,light weight,etc.Dielectric elastomers can be used for driving,energy harvesting,or sensing and have shown great potential in the field of intelligent bionics,soft robotics,biomedicine,etc.In this dissertation,the bio-inspired structures based on dielectric elastomer are studied,and their performances are characterized experimentally.For different bio-inspired structures and their working environment,theoretical models are derived to analyze their nonlinear large deformation behavior and stability under external voltage.The parameters of the bio-inspired structures can also be optimized based on the theoretical models.Firstly,an antagonistic cone dielectric elastomer actuator(ACDEA)is designed based on the working principle of human arm,which is composed of two cone actuators placed symmetrically along the top and fixed by a frame.Based on the thermodynamic framework and the ideal dielectric elastomer model,the theoretical model of the ACDEA is derived.On this basis,the deformation of the ACDEA under different voltages is calculated,the distribution of stretch and stress along longitude and latitude direction on dielectric elastomer membrane are analyzed,and the influence of the height of the ACDEA on its performance is discussed.With the theoretical analysis results,the ACDEA with different heights are fabricated,and their deformation and output force under different voltages are tested.The theoretical results are in good agreement with the experimental results.Inspired by the working principle of human heart,a pump is designed using the ACDEA as the taking structure.The performance of the pump under different voltage and frequency is characterized experimentally.Secondly,a new method is proposed to improve the out-of-plane displacement of the cone dielectric elastomer actuator(CDEA)based on the theoretical results of the ACDEA.The ring-shaped electrode of the CDEA is divided into inner and outer parts,and a higher voltage is applied to the outer ring-shaped electrode to make more effective use of this area.A theoretical model is developed to explain the mechanism of the method.On this basis,the deformation of the CDEA under different applied voltages is calculated,the stress and stretch distribution on the membrane are analyzed,and the effects of the initial voltage of the inner ring-shaped electrode and the position of the electrode boundary on the displacement of the CDEA are discussed.The experimental results are in good agreement with the theoretical results.Both the results show that this method can effectively improve the out-of-plane displacement of the CDEA.A pump module is designed based on the CDEA,and the applicability of this method is verified.Thirdly,a bio-inspired multimodal soft robot is designed based on the simplified locomotion mechanism of caterpillars.The two-degree-of-freedom(2-DOF)dielectric elastomer spring roll actuator was regarded as the deformable body that can elongate,contract,and bidirectional bend.The flexible electroadhesives acted as two feet that can provide required and sufficient frictions whilst crawling on the plane and the wall.The deformation and output force of dielectric elastomer spring roll actuator and the shear adhesive force of flexible electroadhesive under different voltages were tested.Through different control strategies,the crawling,two turning modes and wall climbing of the soft robot are realized,and its performance under different frequencies is characterized.Based on the bidirectional bending characteristics of dielectric elastomer spring roll actuator,the soft robot mimics the looking around behavior of the caterpillar.Through the micro camera fixed on the body,the surrounding during the crawling process can be recorded,which shows the potential in exploration.Finally,aiming at the problem of bio-inspired dielectric elastomer structure working at different temperatures,taking the planar dielectric elastomer actuator as an example,the theoretical model of thermal-mechanical-electrical multi field coupling of dielectric elastomer is derived.In the thermoelastic strain energy,the thermal contributions are introduced.Meanwhile,the temperature dependence of dielectric constant and nonlinear dielectric behavior are considered.The influence of material polarization saturation parameter on the electro-induced deformation is analyzed,and the influence of temperature change on the thermoelectromechanical stability is discussed.The influence of temperature on the crawling performance of the bio-inspired soft robot is preliminarily studied.