Dielectric Elastomer Generators (DEGs) are an emerging technology for the conversion of mechanical into electrical energy. Despite many advantageous characteristics, there are still issues to overcome, including the need for charging at every cycle to produce an electrical output. Self-priming Circuits (SPCs) are one possible solution, storing part of the electric energy output of one cycle to supply as input for the next, producing a voltage boost effect. Until now, studies regarding SPCs neglect to consider how the increasing voltage will create an electromechanical response and affect the DEG when driven by an oscillatory mechanical load. In the present work we model this force-based actuation, including coupling between the DEG and SPC, in order to predict the dynamics of the system. In such cases, the DEG has a mechanical response when charged (actuator behaviour), and as the voltage increases, this actuation-like effect increases the capacitance values that bound the cycle. We show how this inherent nonlinearity yields a reduction in the DEG's capacitance swing and reduces the performance of the SPC, but also self-stabilizes the system. This stability is useful in the design of robust DEG energy harvesters that can operate near to, but not enter, failure mode.

Abstract. One of the main challenges for the practical implementation of dielectric elastomer generators (DEGs) is supplying high voltages. To address this issue, systems using self-priming circuits (SPCs) -which exploit the DEG voltage swing to increase its supplied voltage -have been used with success. A self-priming circuit consists of a charge pump implemented in parallel with the DEG circuit. At each energy harvesting cycle, the DEG receives a low voltage input and, through an almost constant charge cycle, generates a high voltage output. SPCs receive the high voltage output at the end of the energy harvesting cycle and supply it back as input for the following cycle, using the DEG as a voltagemultiplier element. Although rules for designing self-priming circuits for dielectric elastomer generators exist, they have been obtained from intuitive observation of simulation results and lack a solid theoretical foundation. Here we report the development of a mathematical model to predict voltage boost using self-priming circuits. The voltage on the DEG attached to the SPC is described as a function of its initial conditions, circuit parameters/layout, and the DEG capacitance. Our mathematical model has been validated on an existing DEG implementation from the literature, and successfully predicts the voltage boost for each cycle. Furthermore, it allows us to understand the conditions for the boost to exist, and obtain the design rules that maximize the voltage boost.

Dielectric Elastomer Generators (DEGs) have been claimed as one promising technology for renewable mechanical to electrical energy harvesting, due to their lightweight, low cost, and high energy density. Dielectric elastomers have a dual behavior, able to convert electrical energy into mechanical if charged electrostatically and to convert mechanical to electrical energy if stretched and relaxed in a cycle that exploits its capacitance change. During such energy harvesting cycles, the material needs an electrical energy bias to be able to convert mechanical work into electrical energy, which produces an actuator behavior on the DEG that results in losses and decreases its performance. In this paper, we investigate this actuation behavior and its effect on energy harvesting in the DEGs. We compare two different charging methods and show that a constant voltage method can increase the net energy harvested by 5 times, despite the unwanted actuation effect.

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Soft limbs with anisotropic stiffness are common in nature and enable animals to solve a variety of tasks, including locomotion and manipulation. This mixture of hardness and softness enables animals to efficiently control the unpredictable contact forces that occur while performing such tasks. A challenge for soft robotics is to create artificial limbs that mimic natural mixtures of hardness and softness for use as a building block for soft, adaptable robots. This article presents the design of a novel pneumatic limb module with adjustable length and anisotropic stiffness. The artificial limb is designed with a rigid telescopic endoskeleton inside a rubber bellow, which we show is able to resist buckling, while remaining externally soft. Finally, we present the design of a hexapod walker based on the limb units.

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For years, plants have tried to adapt to the environmental changes caused by time, improving and developing their biological structures. Many of these structural and functional properties of plants have great potential for the development of concepts in the field of biomimetics. Recent previous studies have shown that the movement of Mimosa pudica L. is caused by the variation of turgor pressure within the cells of organs motor, that is, the influx and efflux of water by osmosis, generating reversible changes in the shape of the plant. Thus, this article sought, through research and literature references, to carry out a survey of studies related to the seismonastic movements of the plant and its applications in the design of technological innovations. In addition, it presents the development of a pneumatic actuator based on the abstraction of the morphology of the primary pulvinus of the plant and the concept of bioinspired design of the theoretical model based on the technology of soft robots. As a result, the bioinspired actuator model of the plant movement is described. In addition, with a simulation, it was possible to observe that the flexible modules are capable of generating the proposed movement and allow movement of the actuator. With the study, it was possible to understand that the movement of the plant appears as an embryo for the projection of technologies, and that the proposed study appears as the basis for research with pneumatic actuators.

Purpose With recent advances in the field of 3D printing, new prosthetic features have been developed to provide accessibility to patients. However, the mechanisms employed for its performance still need to be better explored. In this article, a study is proposed on the angular variation between the joints of a human finger and a design solution based on soft robotics, in order to guide studies on prosthetic solutions. Methods A literature review was carried out on the applications of pneumatic actuators of soft robotics for the development of hand prostheses. As part of the theoretical aspects, the application of bending actuators that employ the dynamics of the movement of the legs of arachnids was also studied, in order to propose an application in the model. Finally, the angular variation was analyzed during the closing process of the right hand in order to apply the study in the construction of the prosthesis. Results Despite the complexity of moving human fingers, it is possible to develop a prosthetic mechanism that integrates the capabilities of soft actuators and 3D-printed materials. In addition, the angulations of the joints of the index finger vary differently under the same impulse. Conclusion Using the spider's movement mechanism, it is possible to develop a pneumatic actuator integrated with the rigid structures of the printed finger. In addition, the angular variation of the joints of the index finger changes differently under the same stimulus, which allows the application of soft robotics as a resource to mimic human movement.