Effect of Prestrain on the Actuation Characteristics of Dielectric Elastomers

Kinsuk Naskar,Mayank Kumar,Sakrit Hait,Anutsek Sharma,Amit Das,Klaus Werner Stöckelhuber,Gert Heinrich,Injamamul Arief,Sven Wießner

doi:10.3390/polym12112694

Abstract

Dielectric elastomers (DEs) represent a class of electroactive polymers that deform due to electrostatic attraction between oppositely charged electrodes under a varying electric field. Over the last couple of decades, DEs have garnered considerable attention due to their much-coveted actuation properties. As far as the precise measurement systems are concerned, however, there is no standard instrument or interface to quantify various related parameters, e.g., actuation stress, strain, voltage and creeping etc. In this communication, we present an in-depth study of dielectric actuation behavior of dielectric rubbers by the state-of-the-art “Dresden Smart Rubber Analyzer” (DSRA), designed and developed in-house. The instrument allowed us to elucidate various factors that could influence the output efficiency of the DEs. Herein, several non-conventional DEs such as hydrogenated nitrile rubber, nitrile rubber with different acrylonitrile contents, were employed as an electro-active matrix. The effect of viscoelastic creeping on the prestrain, molecular architecture of the matrices, e.g., nitrile content of nitrile-butadiene rubber (NBR) etc., are also discussed in detail.

Highlights

Electroactive polymers (EAPs) are primarily a subset of soft active materials that offer actuation under electric fields [1,2]
Owing to the presence of polar -CN groups and high permittivity (ε = 18), nitrile-butadiene rubber (NBR) are frequently employed as electrode substrates
NBR-based electrodes provide descent actuation due to their high permittivity i.e., ε = 18 and the results showed that, with the gradual increment in ACN content in NBR, the actuation rises from 1% to 3%

Summary

Introduction

Electroactive polymers (EAPs) are primarily a subset of soft active materials that offer actuation under electric fields [1,2]. The EAPs can further be categorized into electronic and ionic EAPs [3]. Dielectric elastomers (DEs) are basically electronic EAPs which offer obvious advantages over relatively ‘slow-response’ ionic counterparts [4]. Active materials derived from DEs are of great value in soft robotics and the development of stretchable electrodes [3,5], owing to their fast responses and considerably high electromechanical efficiency. Dielectric elastomer actuators (DEA) offer large strain potentials, rendering conventional metal or semiconductor strain gauges unattractive. Following the rapid development in robotics and energy sectors, a surge in research on Polymers 2020, 12, 2694; doi:10.3390/polym12112694 www.mdpi.com/journal/polymers

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