Dielectric Elastomer Spring-Roll Bending Actuators: Applications in Soft Robotics and Design.

Dielectric elastomers are novel soft smart material that could deform sustainably when subjected to external electric field. That makes dielectric elastomers promising materials for actuators. In this paper, a spring-roll actuator that would bend when a high voltage is applied was fabricated based on dielectric elastomer. Using such actuators as active parts, the flexible grippers and inchworm-inspired crawling robots were manufactured, which demonstrated some examples of applications in soft robotics. To guide the parameters design of dielectric elastomer based spring-roll bending actuators, the theoretical model of such actuators was established based on thermodynamic theories. The initial deformation and electrical induced bending angle of actuators were formulated. The failure of actuators was also analyzed considering some typical failure modes like electromechanical instability, electrical breakdown, loss of tension and maximum tolerant stretch. Thus the allowable region of actuators was determined. Then the bending angle-voltage relations and failure voltages of actuators with different parameters, including stretches of the dielectric elastomer film, number of active layers, and dimensions of spring, were investigated. The influences of each parameter on the actuator performances were discussed, providing meaningful guidance to the optical design of the spring-roll bending actuators.

The availability of compliant actuators is essential for the development of soft robotic systems. Dielectric elastomers (DEs) represent a class of smart actuators which has gained a significant popularity in soft robotics, due to their unique mix of large deformation (>100%), lightweight, fast response, and low cost. A DE consists of a thin elastomer membrane coated with flexible electrodes on both sides. When a high voltage is applied to the electrodes, the membrane undergoes a controllable mechanical deformation. In order to produce a significant actuation stroke, a DE membrane must be coupled with a mechanical biasing system. Commonly used spring-like bias elements, however, are generally made of rigid materials such as steel, and thus they do not meet the compliance requirements of soft robotic applications. To overcome this issue, in this paper we propose a novel type of compliant mechanism as biasing elements for DE actuators, namely a three-dimensional polymeric dome. When properly designed, such types of mechanisms exhibit a region of negative stiffness in their force-displacement behavior. This feature, in combination with the intrinsic softness of the polymeric material, ensures large actuation strokes as well as compliance compatibility with soft robots. After presenting the novel biasing concept, the overall soft actuator design, manufacturing, and assembly are discussed. Finally, experimental characterization is conducted, and the suitability for soft robotic applications is assessed.

Dielectric elastomer actuators (DEAs) is an emerging soft actuator with attributes of flexibility, large strain, and high energy density. Bistable mechanisms have two force-free stable equilibrium positions in their range of motion, which can hold for a long time without energy consumption. In the present work, a design of bistable system is proposed, consisting of a cross-like shape buckling beam and two conical dielectric elastomer actuators. Analytical model has been developed to analyze the electromechanical coupling behavior of dielectric elastomer and the force-displacement relationship of the cross-like shape buckling beam. The working principle of the bistable conical DEAs is explained in terms of force equilibrium method and internal energy of the system. A bistable dielectric elastomer actuator with a switching force of 0.05 N and a stroke of 5.65 mm is developed to validate the analytical model of the conical DEAs, pre-compressed bistable cross-like beam, and the design.

Soft actuation technology has attracted considerable interest in recent decades, with the light weight, high response speed, and large deformation of dielectric elastomer actuators (DEAs) showing particular promise. DEAs composed of compliant frames and prestrained dielectric elastomers (DEs) can be considered as a soft actuation system, which is termed minimum-energy structure. Most existing DEAs come from a well-known design with a simple configuration but complex design process. In this article, we propose an integrated design method for the actuation and mechanism of DEs based on topology optimization using fat Bezier curves. In this method, the compliant frame is represented by fat Bezier curves, and the prestrained DE is distributed in the region bounded by the curves. This article first describes the theoretical modeling process, and then presents three design examples that validate the optimization algorithm. Finite element analysis (FEA) and experiments are conducted to assess the performance of the optimized configurations. The FEA simulations and experimental results show that the topology optimization algorithm results in DEAs that exhibit the desired motion.

Printed silicone pneumatic actuators for soft robotics

Dielectric elastomers (DEs) are the polymers capable of inducing deformation under electrical stimulation. When subject to a voltage across its thickness, the material reduces in thickness and expands in area. This paper presents a new method to analyze deformation and stress distribution response of the dielectric elastomer actuator (DEA) model under different applied voltage. An equal-biaxial pre-strained circular actuator model was built. The Yeoh strain energy potential and the collocation method are used for describing the large strain actuation response and stress distribution. The study in this paper has shown that: the stress and the stretch distributions in the passive region of the DE actuator depend on the radial distance from the center at the calculation point of the passive region and the magnitude of the applied voltage; with the same excitation applied voltage, we can get a larger deformation actuation by choosing an appropriate pre-stretch ratio; the influence of the non-ideal material has seriously affected the actual deformation of the DE actuators. This analytical model has a reference potential for the design optimization of high performance DEA systems and the model-based control of the DEA robot.

Tendon driven actuators are getting mature in electroactive polymer (EAP) researches. Research and development of the dielectric elastomer (DE) actuator from EAP family, have produced significant progress for decades. Dielectric elastomer is used in this paper to model a micro actuator platform. The parallel platform designing in this paper consists of the kinematics of the platform that is suited for micro structure of the robotic link. This may use for redundant manipulator or snake robot structure. DE is silicon artificial muscles that will actuated by applying voltage which perform a great actuation due to its linear large deflection. A remarkable amount of work has focused on delivering the feasibility of the robotic application of DE material. However, few commercial products equipped with polymer actuators have been introduced in the market, probably because most of the research has been dedicated either to discovering new actuation properties of the polymeric material. Therefore, this polymer is used to model the tendon driven parallel platform actuator for robotic application in this research. In this actuator design, both the upper and lower platforms are of configurations of equilateral triangles with DE cables attached close to the vertices. One DE cable attaches each of the vertices of the lower platform to the vertices directly above it on the upper platform. The three tendons thus enable the platform to exhibit 3 degrees of freedom (DOF). The dielectric polymers are attached with the three edges of the platforms that act like compression-tension cable because of their linear deformation characteristics. Therefore the platform of the DE actuator model is achieved in this research. This actuator can be used to develop redundant robot like snake robot or elephant trunk robot.

A systematic trend analysis of 3D printing techniques used in specific soft robotic elements

Dielectric elastomer is a kind of typical electro-active polymer material. Under external electric field it can produce large electrostriction deformation and possesses the advantages of high elastic energy density, super short response time, high efficiency, and so on. It is widely used in the artificial muscles, facial expressions, actuators, energy harvesters, sensors, robots and Braille display devices, and also shows huge application potential in the aerospace and intelligent bionic areas. We built the free energy of the dielectric elastomer electrical-mechanical coupling system and investigated its constitutive relation and stability behavior. Then we calculated the elastomer’s critical deformation suffering from the voltage. If electrical breakdown, electromechanical instability and snap-through instability can be avoided, the large electrostriction deformation can induce adiabatic temperature change and isothermal entropy change of the dielectric elastomer. We used the entropy-temperature or electric displacement-electric field plane to describe the temperature change and entropy change of dielectric elastomer undergoing large electrostriction deformation. With the influence of temperature, we developed a temperature and deformation coupling thermodynamical free energy model to calculate the electric field induced variation of temperature and entropy in dielectric elastomers. The results should offer great help in guiding the design and fabrication of excellent actuators featuring soft dielectric elastomers.

Dielectric elastomer actuators (DEAs) have emerged as leading candidates for artificial muscles in high-performance soft robotics, simultaneously offering large reversible deformations, excellent mechanical compliance, a fast response, and a high energy density. These features make them ideal for broad applications that require versatile adaptability, lightweight construction, and safe human-machine interactions. Despite their potential, their practical implementation remains hindered by several interrelated challenges, including high driving voltages, poor electromechanical stability, limited power density, and inadequate cycling durability. In addition, scalable fabrication techniques, particularly for large-area compliant electrodes and multilayer device structures, remain underdeveloped. Furthermore, the intrinsic, strongly nonlinear, and rate-dependent behavior of dielectric elastomers complicates accurate modeling and real-time control. This perspective provides a critical overview of recent developments in the material design, manufacturing strategies, and dynamic modeling of DEAs and identifies the key barriers and opportunities across these comprehensive domains. This perspective aims to accelerate the advancement of high-performance DEA systems and inspire innovative solutions for their integration into real-world soft-robot applications.

Dielectric elastomer actuators are ideal drivers for next-generation soft robots due to their large electroactive deformations. However, conventional dielectric elastomers suffer from insufficient breakdown strength and high mechanical loss, which limits their ability to meet the demanding requirements of advanced robotics for high energy and power densities. Herein, we propose a versatile strategy for incorporating organic molecular semiconductors into the dielectric elastomer network. This design simultaneously achieves high breakdown strength (82 V μm-1), desirable modulus, elasticity, and large electro-actuation strain (174%). Consequently, the optimized elastomer delivers a high energy density (169 J kg-1) and an ultrahigh power density (3000 W kg-1), surpassing natural muscle by 8-fold and outperforming all reported dielectric elastomers. A demonstrated light-emitting, fast-moving soft robot further highlights the material's multifunctional application potential.

Advancements and challenges in dielectric elastomer actuator-based biomimetic mobile robots

Dielectric elastomers are soft, lightweight, and highly deformable electroactive polymers that undergo large deformations when subjected to mechanical and electrical loading. This unique property makes them promising candidates for applications in artificial muscles, soft robotics, biomedical actuators, and sensors. In this study, the large deformation behavior of a flat, circular dielectric elastomer membrane, clamped at the boundary, is investigated under the combined influence of lateral pressure and an applied electric potential across its thickness. The resulting model provides a framework for predicting deformation profiles and electromechanical stability limits in dielectric elastomer actuators.

Living organisms intertwine soft (e.g., muscle) and hard (e.g., bones) materials, giving them an intrinsic flexibility and resiliency often lacking in conventional rigid robots. The emerging field of soft robotics seeks to harness these same properties to create resilient machines. The nature of soft materials, however, presents considerable challenges to aspects of design, construction, and control—and up until now, the vast majority of gaits for soft robots have been hand-designed through empirical trial-and-error. This article describes an easy-to-assemble tensegrity-based soft robot capable of highly dynamic locomotive gaits and demonstrating structural and behavioral resilience in the face of physical damage. Enabling this is the use of a machine learning algorithm able to discover effective gaits with a minimal number of physical trials. These results lend further credence to soft-robotic approaches that seek to harness the interaction of complex material dynamics to generate a wealth of dynamical behaviors.

Dielectric elastomer (DE) materials, a category of electroactive polymers, can be used to design actuators that are flexible, resilient, lightweight, and durable. However, due to the uncertainties in its actuation dynamics, DE actuators always rely on feedback control to perform accurate and safe operations. In this paper, a tubular dielectric elastomer actuator (DEA) with self-sensing capability is developed. It does not require external devices to measure displacement for feedback control. The displacement of the actuator is controlled using a proportional-integral controller with the capacitance measured at high probing frequency as the self-sensing mechanism component of the actuator. By superimposing actuation and probing voltage and applying them to the DE tube, the actuation voltage activates the movement of the DE tube and the probing voltage is used for self-sensing. Fast Fourier Transform (FFT) is then used to filter a given frequency of the probing current and voltage and then calculate the capacitance from the probing current and voltage during each time window. With the relationship between capacitance and displacement of the DE tube, the displacement output is estimated online and self-sensing without an external sensor is achieved. The self-sensing signal is then used as a feedback signal in a closed-loop design to follow a reference signal for tracking. The experimental results validate the self-sensing of the DE actuator in feedback control.