Underwater Bending Actuator Based on Integrated Anisotropic Textile Materials and a Conductive Hydrogel Electrode

Gerald Gerlach,Martina Zimmermann,Konrad Katzer,Sascha Pfeil,Johannes Mersch,Cornelia Breitkopf,Alice Mieting,Rebecca Grün

doi:10.3390/act10100270

Gerald Gerlach, Martina Zimmermann + Show 6 more

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https://doi.org/10.3390/act10100270

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Abstract

Electroactive polymers (EAPs), especially dielectric elastomer actuators (DEAs), belong to a very promising and emerging class of functional materials. While DEAs are mostly utilized to rely on carbon-based electrodes, there are certain shortcomings of the use of carbon electrodes in the field of soft robotics. In this work we present a fish-like bending structure to serve as possible propulsion element, completely avoiding carbon-based electrodes. The presented robot is moving under water, using a particularly tailored conductive hydrogel as inner electrode and a highly anisotropic textile material to manipulate the bending behavior of the robot. The charge separation to drive two DEAs on the outsides of the robot is provided by the conductive hydrogel while the surrounding water serves as counter electrode. To characterize the hydrogel, tensile tests and impedance spectroscopy are used as measurement methods of choice. The performance of the robot was evaluated using a digital image correlation (DIC) measurement for its bending deflections under water. The developed fish-like robot was able to perform a dynamic bending movement, based on a tri-stable actuator setup. The performed measurements underpin the sufficient characteristics for an underwater application of conductive hydrogel electrodes as well as the applicability of the robotic concept for under water actuations.

Highlights

We demonstrated a fully functional fish fin robot that utilizes a conductive hydrogel as highly conductive and very elastic electrode material
By utilizing the outstanding properties of the hydrogel in combination with the used anisotropic textile-elastomer composite, an actuator structure is presented that can be used as a possible propulsion element for underwater applications
The developed robotic concept presents an approach for possible enhancements of the electro-mechanical properties of the dielectric elastomer actuators (DEAs) and to adjust the robotic concept to aqueous surroundings

Summary

Introduction

Current developments in the field of EAPs are continuously creating new concepts and drive solutions with remarkable innovative momentum. While a lot of effort is already put into optimizing their force output and efficiency, the demand on reliable electrodes allowing large deformations seems still not sufficiently solved. Established robotic concepts using DEAs mostly rely on carbon-based electrodes [1,2]. Such electrodes use a base material with infiltrated conductive particles like carbon black [3] or carbon nanotubes [4], compatible with the dielectric material. The existing trade-off with carbon-based electrodes lies in complementary mechanical (high deformations) and electrical (sufficient conductivity) properties. To provide a solution for that shortcoming, Carpi et al demonstrated the feasibility of using conductive liquid electrodes for DEAs [5]

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