Ajeet Kumar

Dielectric properties govern the electromechanical response of electroactive polymer (EAP) actuators and the conversion efficiency of EAP generators, with the dielectric constant playing a particularly critical role in determining how effectively such sensors, actuators, and generators perform. This study examines how low frequency, temperature, and mechanical prestretch jointly influence the dielectric constant of two candidate elastomers: acrylic (VHB 4910, manufactured by 3M, USA) and natural rubber (Oppoband 8001 manufactured by OPPO Medical Inc., USA). Measurements were carried out from 1 Hz to 1 MHz over a temperature range of −80 °C to 60 °C and across different configurations of prestretch states (equal biaxial, unequal biaxial and uniaxial prestretches) from λ₁ × λ₂ = 1 × 1 to 5 × 5. In both elastomers, the dielectric constant decreased with increasing frequency and with temperature shifts away from the optimum, reflecting dielectric relaxation, and declined steadily with increasing prestretch due to restricted dipole reorientation. VHB 4910 showed markedly greater sensitivity, with its permittivity falling by 32.53% at 0 °C compared with only 14.23% for Oppoband 8001, a contrast attributable to the differing polarity of the two polymer backbones. Glass transition temperatures (T_g) were determined from the loss factor peaks obtained experimentally from dynamic mechanical analysis (DMA), giving values of −42 °C for VHB 4910 and −68 °C for Oppoband 8001. These findings establish practical operational temperature limits to guide material selection, particularly for soft robotic applications.

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.

The electromechanical performance of a dielectric elastomer (DE) is greatly influenced by the dielectric strength of the elastomeric materials. The dielectric strength of an elastomer profoundly depends on the state of mechanical stretch. In this work, the stretch-dependent dielectric strength for DE is measured for all possible modes of stretches using compliant electrodes. Dielectric breakdown measurement using compliant electrodes considers voltage-induced deformation, which reflects the actual working condition energy transduction. Hence, the measured strength is for a meaningful value of a working DE. Capacitive extensometry and optical method are the two leading methods for the same. We compare the extensometry and optical methods in estimating the true value of dielectric breakdown strength of DEs at high pre-stretches. Furthermore, we propose a modified thickness stretch-based power law for the dielectric breakdown strength. Using the capacitive extensometry method, we verify the model on comprehensive experimental data on three types of elastomers, i.e., acrylic, silicone, and natural rubber. This work proposes a general framework for estimating the meaningful stretch-dependent dielectric strength of DEs.

Dielectric elastomer generator (DEG) comprises of soft and stretchable capacitive transducer. The DEG experiences a change in capacitance and provides a voltage gain ( $G$ ) with an applied mechanical excitation. This article interprets DEG as a machine that involves a cyclic change of finite-state transducer capacitances to transmit or modify energy. In this study, a relative analysis of capacitances associated with the DEG transducer is introduced and analyzed to improve the DEG performance. This article focuses on defining a relationship between the material stretch ( $\lambda$ ) and finite-state capacitances associated with the DEG transducer. The estimation of stretch-imposed DEG capacitance under mechanical excitation is well investigated. Eventually, the analysis is experimentally validated with the developed mechanical prototype. For distinct transducer deformation, the associated capacitances are estimated with the capacitive extensometer method and the stretch ( $\lambda$ ) is calculated. Moreover, for effective energy conversion, the finite state capacitance variation is maintained large enough to provide a relatively high voltage gain. Experimental results show that for 70% increase in capacitance difference at the DEG makes the specific energy increase from 3.5 to $11.5~\mu \text{J}$ /g. This study could lead the DEG as an alternative power source for low-power electronic gadgets.