Dielectric Elastomer Generators Research Articles

Dielectric Elastomer Generators: Recent Advances in Materials, Electronic Circuits, and Prototype Developments

The ongoing climate crisis requires innovative methods to maximize renewable and sustainable energy resources. There have been advancements in harvesting energy from ambient motions such as wind, ocean waves, and human movements. Dielectric elastomer generators (DEGs) are a promising option for energy harvesting due to their high energy density and compatibility with low‐frequency oscillations. This review provides an in‐depth overview of DEGs, including electroactive materials, electromechanical characterization, electronics for harvesting, interfacing circuits, prototypes, and challenges. DEGs have the potential to play a significant role in decarbonizing energy for both small‐ and large‐scale applications using ambient energy sources.

Optimizing energy density in dielectric elastomer generators: a reliability-dependent metric

Abstract Dielectric elastomer generators (DEGs) are soft transducers capable of converting mechanical energy into electrostatic energy. Increasing the mechanical stretch amplitude and the electric field imposed to the DEG leads to higher energy conversion at the cost of a reduced lifetime. Here, mechanical fatigue and electrical degradation were assessed on a silicone-based DEG, and the outcome was used to build an electro-mechanical reliability model. A novel metric, termed levelized energy density, has been introduced to carefully balance the conflicting objectives of high energy output and long-term reliability. Through a multi-dimensional anaylsis of this index, the optimal operating parameters (stretch amplitude and electric field) that maximize energy conversion can be derived. Energy densities reported in literature are generally obtained after pushing the DEG close to their intrinsic limits for a limited number of cycles. In our approach, more realistic values in the endurance domain are presented, which typically leads to a 9-fold decrease in energy density for a design life of 1 million cycles. This article not only addresses the challenge of optimizing DEG performance but also emphasizes the importance of considering realistic operational conditions to enhance reliability, ultimately contributing to the practical and sustainable deployment of these soft transducers in various applications.

Energy harvesting from a fiber-constrained dielectric elastomer generator embedded into a novel floating wave energy harvester

Abstract With the increasing energy demand and growing concern about greenhouse gases emissions from fossil fuel combustion, converting the ocean wave energy into the electrical energy has emerged as a promising and sustainable solution. This paper proposes a novel floating ocean wave energy harvester based on the fiber-constrained dielectric elastomer generator (DEG) arrays and investigates the energy harvesting (EH) performance of the fiber-constrained DEG embedded into the harvester. A theoretical analysis model of the fiber-constrained DEG describing the free relaxation process is developed and verified by the existing experimental data. On this basis, the electrical energy and conversion efficiency of the fiber-constrained DEG are comprehensively analyzed under diverse system parameters, aiming to explore the feasible methods for performance improvement. Results show that both the electrical energy and conversion efficiency are enhanced by shortening the cycle period, boosting the output voltage, and increasing the time ratio of the rising segment in a cycle period. Variations of the electrical energy and conversion efficiency with the input voltage exhibit the non-monotonic behavior. In addition, at low input voltage, enlarging the maximum stretch ratio improves the EH performance, while at high input voltage, the overlarge maximum stretch ratio goes against the performance improvement. The average output power of the harvester with different lengths of rods in its displacement magnifying mechanism is also investigated. Results show increasing the rod length can improve the average output power. In addition, results can help to provide a guidance for designing a high-performance DE-based floating wave energy harvester.

Advancements and Future Prospects in Ocean Wave Energy Harvesting Technology Based on Micro-Energy Technology.

Marine wave energy exhibits significant potential as a renewable resource due to its substantial energy storage capacity and high energy density. However, conventional wave power generation technologies often suffer from drawbacks such as high maintenance costs, cumbersome structures, and suboptimal conversion efficiencies, thereby limiting their potential. The wave power generation technologies based on micro-energy technology have emerged as promising new approaches in recent years, owing to their inherent advantages of cost-effectiveness, simplistic structure, and ease of manufacturing. This paper provides a comprehensive overview of the current research status in wave energy harvesting through micro-energy technologies, including detailed descriptions of piezoelectric nanogenerators, electromagnetic generators, triboelectric nanogenerators, dielectric elastomer generators, hydrovoltaic generators, and hybrid nanogenerators. Finally, we provide a comprehensive overview of the prevailing issues and challenges associated with these technologies, while also offering insights into the future development trajectory of wave energy harvesting technology.

Trapping Ions to Enhance High-Field Energy Harvesting Performance by Filling Polar Macromolecular Dielectrics.

In the quest for sustainable and renewable energy sources, researchers and engineers have explored innovative technologies to harvest energy from various environmental sources. Dielectric elastomer generators (DEGs) with high energy harvesting performance have been proven to be promising energy collectors, but achieving a high dielectric constant (ε') and low electrical conductivity (EC) under high electric fields of dielectric elastomer (DE) simultaneously is a struggle, which poses significant challenges. In this study, high-content carboxyl group-grafted liquid polybutadiene (HCPB) is synthesized and then adopted as an organic dielectric filler to blend and cocross-link with a butadiene rubber (BR) matrix to prepare DE composites with high energy harvesting performance. The introduction of carboxyl groups enhances polarization while trapping free Al3+ in the matrix, which revolutionarily achieves a significant increase in ε' under extremely low EC. Ultimately, the contradiction between increased ε' and decreased EC under high electric fields is reconciled, resulting in a 30 HCPB/BR composite with high energy density (w = 91.9 mJ/cm3) and fine power conversion efficiency (PCE = 24.1%). This advancement paves the way for the development of HCPB/BR composite-based DEGs with enhanced ε' and energy harvesting performance.

Ocean wave energy harvesting: Utilizing buoy float to induce dielectric elastomer deformation and electret vibration for power generation

The dielectric elastomeric polymer material, characterized by its high energy output, resilience, mechanical compliance, lightweight, damage tolerance, and low cost, demonstrates significant potential as an innovative sustainable energy converter. It seamlessly adapts to the ever-changing climatic conditions of the ocean, converting the violent impacts of wave kinetics into electrical energy. This paper proposed a viable electret and dielectric elastomer wave energy harvester to convert ocean wave energy into electricity and aims to achieve self-priming operation in the conjugate components. The output voltage from the electret also functions as the bias voltage for the dielectric elastomer, based on the intrinsic variable capacitance electric translation principle. The dielectric elastomer's deformation, equivalent to variable capacitance, successfully converted the mechanical energy from the ocean waves into electrical energy. The ocean wave energy conversion is evaluated using a system-level approach, incorporating theoretical, simulation, and experimental models. In addition, electric power generation is assessed with parameters such as output voltage, electret surface potential, and bias voltage. Essentially, the electric energy produced by the electret generator can serve as the bias voltage source for the dielectric elastomer generator, providing a self-sustaining solution for ocean wave energy harvesting. The innovative power device envisions various potential configurations for ocean-based power generation.

Advantages of a novel truncated cone DE-air generator in energy conversion

Abstract Harvesting energy from ambient environments such as vibrations is a feasible approach to selfpower low powered electric devices. T- he dielectric elastomer generator (DEG) is a type of novel electrostatic generator with superior vibration energy harvesting (EH) performance. On the basis of traditional DEGs, a new concept of dielectric elastomer (DE)-air generator (DEAG), which contains the air layer and the DE membrane (DEM) as a composite dielectric layer, is proposed in this paper for the first time. Inspired by a classical truncated cone DEG (TC-DEG) concept, the novel truncated cone DEAG (TC-DEAG) is designed and comprehensively studied. Compared with the TC-DEG, the proposed TC-DEAG provides the larger capacitance ratio, leading to superior electrical output. The energy conversion mechanisms of both the TC-DEG and the TC-DEAG under a regular linear reciprocating excitation are analyzed theoretically by deducing the deformation condition of the DEM and the electrical outputs. Through measuring the capacitance of the DEM under deformations and testing the output voltage of the fabricated generators, the proposed theoretical models and predictions are verified. Moreover, numerical simulations based on the verified theoretical model are conducted to reveal the influences of some important system parameters on the EH performances of both generators, providing guidelines for the performance improvement of the generators.

A Marine Experiment Using Dielectric Elastomer Generators and Comparative Study with Actual Measured Values and Theoretical Values

Power generators using dielectric elastomer (DE) transducers are inexpensive, highly efficient, lightweight, stackable, and also easy to install. Therefore, it is considered optimal for an eco-energy society and is attracting attention as a renewable energy device. In particular, DE wave power generators are characterized by the fact that it is not limited by the direction and size of waves, which is a problem with existing wave power generation. This paper presents an accurate method for measuring the energy generated by a DE generator (DEG) and compares it with the theory value obtained by calculation. The electrode materials actually used in this study were a variety of carbon-based materials (including muti-wall carbon nanotube (MWCNT) and singe-wall carbon nanotubes (SWCNT)), and the performance of DEs using these materials was compared. Furthermore, ocean experiments in actual sea areas using DEG were also conducted, and the energy conversion rate was calculated based on the electrical results.

Hydroelastic modelling of a deformable wave energy converter including power take-off

Given the advantages of flexible wave energy converters (FlexWECs), such as deformation-led energy harnessing and structural loading compliance, there has been a significant interest in FlexWECs in both academia and industries. To simulate the FlexWEC interaction with ocean surface waves, a 3D computational fluid-structure interaction approach is developed in this study. The fluid and solid governing equations are discretized using finite difference and finite element methods, respectively. An immersed boundary method is used to couple the two independent grid systems. A novel numerical technique is introduced to model the dielectric elastomer generator (DEG) as the power take-off (PTO). The wave energy capture performance is analysed for different PTO configurations and at various wave conditions. Based on the obtained results, the PTO damping coefficient and the relative wavelength range that maximizes the capture width ratio (CWR) are determined. The wavefield results also reveal the presence of wave-height enhancement and attenuation points around a single FlexWEC, providing potential site selection references when deploying multiple FlexWECs in an array.

Modeling and control of planar dielectric elastomer energy harvester

Dielectric Elastomer Generators (DEGs) have been used as mechanical-electrical transducers in energy harvesting systems. However, material safety assurance control, which prevents dielectric elastomer (DE) failures, is not fully investigated. Since various DEG configurations share common failure modes, incorporating these modes into the system is crucial for extending DEG lifetime and improving output power capacity of DE energy harvesters. This paper develops a physics-based model for a planar DE energy harvester and material failure modes identified through analytical analysis of the model. A real-time algorithm for internal safety control is developed to allow operation within a broader feasible region while preventing electrical breakdown (EB), electromechanical instability (EMI), loss of tension (LT), or rupture by stretch (RS). The algorithm prioritizes safety control when the feasible space is violated and allows primary control when operating within the safe space. As a step towards prototyping of an energy harvester using a DE, a prototype concept model is outlined. By using the safety control algorithm, energy harvesting output power is maximized without violating material safety rules, making it applicable to various energy source conversions like human motion, tidal wave, and wind energy.

Synthesis of Bottlebrush Polymers with Spontaneous Self-Assembly for Dielectric Generators.

Cross-linked bottlebrush polymers received significant attention as dielectrics in transducers due to their unique softness and strain stiffening caused by their structure. Despite some progress, there is still a great challenge in increasing their dielectric permittivity beyond 3.5 and cross-linking them to defect-free ultrathin films efficiently under ambient conditions. Here, we report the synthesis of bottlebrush copolymers based on ring-opening metathesis polymerization (ROMP) starting from a 5-norbornene-2-carbonitrile and a norbornene modified with a poly(dimethylsiloxane) (PDMS) chain as a macromonomer. The resulting copolymer was subjected to a postpolymerization modification, whereby the double bonds were used both for functionalization with thiopropionitrile and subsequent cross-linking via a thiol-ene reaction. The solutions of both bottlebrush copolymers formed free-standing elastic films by simple casting. DMA and broadband impedance spectroscopy revealed two glass transition temperatures uncommon for a random copolymer. The self-segregation of the nonpolar PDMS chains and the polynorbornane backbone is responsible for this and is supported by the interfacial polarization observed in broadband impedance spectroscopy and the scattering peaks observed in small-angle X-ray scattering (SAXS). Additionally, the modified bottlebrush copolymer was cross-linked to an elastomer that exhibits increased dielectric permittivity and good mechanical properties with significant strain stiffening, an attractive property of dielectric elastomer generators. It has a relative permittivity of 5.24, strain at break of 290%, elastic modulus at 10% strain of 380 kPa, a breakdown field of 62 V μm-1, and a small actuation of 5% at high electric fields of 48.5 V μm-1. All of these characteristics are attractive for dielectric elastomer generator applications. The current work is a milestone in designing functional elastomers based on bottlebrush polymers for transducer applications.

Largely Enhanced Energy Harvesting Performance of Silicone-Based Dielectric Elastomer Generators through Controlling the Uniaxial Device Structure

Largely Enhanced Energy Harvesting Performance of Silicone-Based Dielectric Elastomer Generators through Controlling the Uniaxial Device Structure

A 3D coordination polymer of Cd(II) with conformationally flexible mixed ligands as an active filler for silicone elastomers

The electronic configuration of d10 metals enables for a wide range of coordination numbers and geometries which, together with the use of mixtures of ligands for their coordination, allows fine-tuning of the properties of the complexes formed. By treating Cd(ClO4)2 with 1,3-bis(carboxypropyl)tetramethyldisiloxane (H2Cx) and 4,4′-azopyridyne (AzPy) in solution, a 3D coordination polymer, [Cd(Cx)(AzPy)·1.85H2O]n (1), was mostly formed. The compound was investigated by elemental and spectral analysis, as well as by powder and single crystal X-ray diffraction. Thermal behavior of compound 1 was evaluated by TGA and DSC, while the moisture behavior was studied by dynamic vapor sorption (DVS) analysis. Compound 1 contains a five-dentate Cx2− ligand with Cd atoms in a pentagonal-bipyramidal geometry, as determined by X-ray analysis. The conformational flexibility of the ligands allows the establishment of all possible intermolecular interactions in a very dense packing, the resulting structure having an extremely low free volume (14.8%). The compound is hydrophobic, adsorbing up to 2.4 wt% water vapor, thermally stable up to 160 °C, and has a phase transition around 6 °C, which, based on analysis by polarized optical microscopy (POM), is considered as a second-order crystal-to-crystal transition, facilitated by the mobility of the siloxane fragment. Due to the constraints imposed by the covalent 3D architecture, the conformational photoisomerization of 1 is extremely limited, as indicated by UV–Vis spectroscopy studies on solutions with solvents of different polarities as well as dielectric spectroscopy studies on silicone composites in which it is in solid state with 5 and 20 wt% loading. Instead, it was found that compound 1 significantly increases the dielectric strength of the resulting materials (up to 46 V/μm compared to 18 V/μm in the empty matrix) by incorporating it as a filler, making them suitable for dielectric elastomer generators, as the results of theoretical calculations indicate. In the purification process, a 2D coordination polymer, [Cd(Cx)(AzPy)·H2Cx]n (2), was also identified in traces.

Largely Enhanced Service Life and Energy Harvesting Stability of Dielectric Elastomer Generator by Designing and Optimizing Compliance of Electrodes.

Dielectric elastomer generator (DEG), which consists of a dielectric elastomer (DE) film sandwiched between two flexible electrodes (FEs), has the advantages of lightweight, high energy density, and high energy conversion efficiency, providing a simple and feasible solution for harvesting energy from human motion or nature. As crucial constituents of DEG, FEs are expected to possess excellent conductivity and compliance. Nevertheless, there is currently no quantitative characterization method for FE compliance. In addition, the impact mechanism of FE compliance on the energy harvesting performance and fatigue life of the DEG remains unclear. In this study, the dynamic mechanical property (DMP) was used to assess the compliance of FEs, and the quantitative characterization method of FE compliance was proposed. A series of silicone rubber electrodes (SREs) with different DMPs and compliance were designed and prepared, and the impact mechanism of FE compliance on the energy harvesting stability and fatigue life of the DEG was investigated. The results indicate that the key to achieving excellent FE compliance lies in reducing the difference in the magnitude of the complex modulus and phase angle between the FEs and DE, which can significantly reduce interfacial friction and extend the fatigue life of DEG. Benefiting from the enhanced FE compliance, the fatigue life and full-life energy density of the DEG device increase by 20.3 times and 26.4 times, respectively, compared with those of the commonly used carbon-based electrodes.

Highly stretchable and self-healing SEBS-PVDF composite films for enhanced dielectric elastomer generators

Highly stretchable and self-healing SEBS-PVDF composite films for enhanced dielectric elastomer generators

An Integrated Charge Excitation Alternative Current Dielectric Elastomer Generator for Joint Motion Energy Harvesting

AbstractJoint movement is a plentiful source of energy in living organisms; however, it is challenging to harvest due to its multidirectional nature, and effective technologies for harnessing this energy are lacking. In this study, a novel approach is presented to harvest joint motion energy by combining an alternating current dielectric elastomer generator (AC‐DEG) with an electret nanogenerator (ENG). The ACENG‐DEG, utilizing ion hydrogel electrodes and ENG, exhibits remarkable stretchability (860%) and efficiently converts mechanical energy into electrical energy through a stretch‐based mechanism. With only 37 cycles, the device reaches a saturation voltage of 1.18 kV and generates an output charge of 1.96 µC per cycle. Notably, the charge output response speed is approximately four times faster than that of traditional AC‐DEGs. The proposed strategy for harvesting human mechanical energy in this study represents a promising pathway for developing high‐performance energy harvesting devices and self‐powered systems.

Superstretchable Liquid-Metal Electrodes for Dielectric Elastomer Transducers and Flexible Circuits.

Dielectric elastomer transducers (DETs), with a dielectric elastomer (DE) film sandwiched between two compliant electrodes, are highly sought after in the fields of soft robotics, energy harvesting, and human-machine interaction. To achieve a high-performance DET, it is essential to develop electrodes with high conductivity, strain-insensitive resistance, and adaptability. Herein, we design an electrode (Supra-LMNs) based on multiple dynamic bond cross-linked supramolecular networks (Ns) and liquid metal (LM), which realizes high conductivity (up to 16,000 S cm-1), negligible resistance changes at high strain (1.3-fold increase at 1000% strain), instantaneous self-healability at ambient temperature, and rapid recycling. The conductive pathway can be activated through simple friction by transmitting stress through the silver nanowires (AgNWs) and cross-linking sites of LM particles. This method is especially attractive for printing circuits on flexible substrates, especially DE films. Utilized as dielectric elastomer generator (DEG) electrodes, it reduces the charge loss by 3 orders of magnitude and achieves high generating energy density and energy conversion efficiency on a low-resistance load. Additionally, serving as sensor (DES) and actuator (DEA) electrodes, it enables a highly sensitive sensing capability and complex interaction.

Dielectric Breakdown Strength of PDMS Elastomers after Mechanical Cycling

PDMS-based composites such as silicone elastomers are commonly found in high-voltage engineering, especially in outdoor insulation as coatings or structural elements or at interfaces between network elements, such as cable sealing ends (CSE). They are also promising prospects for dielectric elastomer generators (DEG), which are retrieving electrostatic energy from large strain amplitudes. The upper limit of energy conversion from these transducers is determined by the dielectric breakdown strength (DBS). Therefore, developing reliable systems that operate under high electric fields and variable repeated strains requires a thorough understanding of the mechanisms behind electrical breakdown and its coupling to mechanical cycling. In this study, the effect of Mullins damage and mechanical fatigue on silicone elastomers has been investigated. An electro-mechanical instability model that considers cyclic softening allows for predicting the evolution of the breakdown strength depending on the loading history. The results highlight the importance of the “first cycle,” where up to a 30% reduction in the mean DBS was measured. However, subsequent mechanical fatigue only marginally contributes to the degradation, which is a promising perspective for the long-term performance of any silicone elastomer as long as the precise impact of the first cycle is known.

Nonlinear dynamics and chaos control of circular dielectric energy generator

The current study focuses on the nonlinear dynamics of the dielectric elastomer generator (DEG). To begin with, we will go through DEG’s operating principles, parameters, materials, and deformation modes. On this basis, the dynamical modeling for the nonlinear behavior of the DEG system is described, and the second-order nonlinear ordinary differential equation representing radially symmetric motion is derived using Hamilton’s variational principle. A static applied electric field allows the DEG system to attain two equilibrium states: thick and thin. The effects of the stiffening phenomenon on the dynamics of the DEG system are investigated. The system converges to a stable equilibrium point under constant loads, and the convergence position and velocity are closely related to both the initial states. Subjected to periodic loads, certain phenomena such as quasiperiodicity and chaos are detected, and the chaotic phenomena are explored using the bifurcation diagram and 0-1 chaos test. Furthermore, parametric studies are carried out using numerical analyses to demonstrate the influence of load amplitude and external frequency on the dynamics of the DEG system. Once the DEG enters the chaotic regime, the chaotic zone is transformed into a stable manifold using established chaos control techniques such as system parameter change and parametric perturbation. However, because these techniques require changes in system design, we proposed a chaos control by using a non-linear controller, specifically, adaptive integral backstepping sliding mode control (AIBSMC) as one demonstrative candidate. The controller also enables the DEG system to follow motion along a predefined trajectory. The current work may be expected to substantially impact the future design and performance of energy harvesters.

Size effect and electrical ageing of PDMS dielectric elastomer with competing failure modes

Large-scale dielectric elastomer generators dielectric elastomer generators (DEGs) such as those employed in wave energy converter projects require a significant volume of electrically stressed materials. Meanwhile, predictions of energy output from such systems are generally extrapolated from electrical and mechanical breakdown measurements performed on small scale samples, where the presence of small defects can be extremely small. This can lead to overly optimistic upscaled predictions for the performance and reliability of full-scale devices. In this study, multilayer DEGs were prepared to evaluate the dielectric breakdown strength of thin polydimethylsiloxane PDMS elastomer at different values of active areas. The results indicated the presence of two separate breakdown mechanisms resulting in an enhanced size effect and a reduced reliability for the larger samples. Electrical ageing tests were performed on three different sample geometries and the dielectric breakdown strength was found to be marginally affected by the time under stress. A Weibull competing failure model was applied to the distribution of experimental breakdowns and electrical reliability was accurately modeled over more than four decades of variation in the electrode area.