Characterizations and Inkjet Printing of Carbon Black Electrodes for Dielectric Elastomer Actuators.

Dielectric elastomer actuators (DEAs) have been proposed as a promising technology for developing soft robotics and stretchable electronics due to their large actuation. Among available fabrication techniques, inkjet printing is a digital, mask-free, material-saving, and fast technology, making it versatile and appealing for fabricating DEA electrodes. However, there is still a lack of suitable materials for inkjet-printed electrodes. In this study, multiple carbon black (CB) inks were developed and tested as DEA electrodes inkjet-printed on acrylic membranes (VHB). Triethylene glycol monomethyl ether (TGME) and chlorobenzene (CLB) were selected to disperse CB. The inks' stability, particle size, surface tension, viscosity, electrical resistance, and printability were characterized. The DEA with Ink-TGME/CLB (mixture solvent) electrodes obtained 80.63% area strain, a new benchmark for the DEA actuation with CB powder electrodes on VHB. The novelty of this work involves the disclosure of a new ink recipe (TGME/CLB/CB) for inkjet printing that can obtain stable drop formations with a small nozzle (17 × 17 µm), high resolution (∼25 µm, approaching the limit of drop-on-demand inkjet printing), and the largest area strain of DEAs under similar conditions, distinguishing this contribution from the previous works, which is important for the fabrication and miniaturization of DEA-based soft and stretchable electronics.

Modelling dielectric elastomer circuit networks for soft biomimetics.

In order to obtain entirely soft bio-inspired robots, fully soft electronic circuits are needed. Dielectric elastomers (DEs) are electroactive polymers that have demonstrated multifunctionality. The same material can achieve different tasks like actuation, sensing, or energy harvesting. It has been shown that basic logic and memory functions can be realized with similar soft structures by combining multiple DE actuators and DE switches. Thus it would be possible to build, with the same materials and processes, a soft structure that mimics a biological being with all these capabilities. This contribution is focused on the modelling of the aforementioned soft electro-mechanical circuit networks. It is here reported the building process of a comprehensive SIMULINK model including the electro-mechanical behaviour of DE logic units and their interconnections. Conventional models deal with a single aspect of DEs, generating complex finite-element simulations. This contribution, based on a former model for an inverter-based DEO, shows how to integrate these various mathematical models and, with the help of direct measurements, create a software representation of DE circuit networks. This work is intended to demonstrate the validity of a recently introduced model and apply it to more complex circuit networks that have a higher number of components. Since, at the present state, the building processes are by hand, adding components generates more variability due to sample-to-sample variation and human error. Despite this, the model still shows a qualitatively good prediction of the devices' behaviour. Furthermore, the introduction of new materials and automatic processes will help to reduce this variability, allowing the model to reach even better performance.