Assessing the degradation of compliant electrodes for soft actuators.

We present an automated system to measure the degradation of compliant electrodes used in dielectric elastomer actuators (DEAs) over millions of cycles. Electrodes for DEAs generally experience biaxial linear strains of more than 10%. The decrease in electrode conductivity induced by this repeated fast mechanical deformation impacts the bandwidth of the actuator and its strain homogeneity. Changes in the electrode mechanical properties lead to reduced actuation strain. Rather than using an external actuator to periodically deform the electrodes, our measurement method consists of measuring the properties of an electrode in an expanding circle DEA. A programmable high voltage power supply drives the actuator with a square signal up to 1 kHz, periodically actuating the DEA, and thus stretching the electrodes. The DEA strain is monitored with a universal serial bus camera, while the resistance of the ground electrode is measured with a multimeter. The system can be used for any type of electrode. We validated the test setup by characterising a carbon black/silicone composite that we commonly use as compliant electrode. Although the composite is well-suited for tens of millions of cycles of actuation below 5%, we observe important degradation for higher deformations. When activated at a 20% radial strain, the electrodes suffer from important damage after a few thousand cycles, and an inhomogeneous actuation is observed, with the strain localised in a sub-region of the actuator only.

[1]  Samuel Rosset,et al.  Inkjet printing of carbon black electrodes for dielectric elastomer actuators , 2017, Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring.

[2]  Ehsan Omidi,et al.  Multiple Mode Spatial Vibration Reduction in Flexible Beams Using H2- and H∞-Modified Positive Position Feedback , 2015 .

[3]  M. Ghaffarian Niasar,et al.  Mechanical stretch influence on lifetime of dielectric elastomer films , 2017, Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring.

[4]  H. Shea,et al.  Improved electromechanical behavior in castable dielectric elastomer actuators , 2013 .

[5]  Samuel Rosset,et al.  The need for speed , 2012, Smart Structures.

[6]  Zhigang Suo,et al.  Highly stretchable and transparent ionogels as nonvolatile conductors for dielectric elastomer transducers. , 2014, ACS applied materials & interfaces.

[7]  Joseph Eckerle,et al.  From boots to buoys: promises and challenges of dielectric elastomer energy harvesting , 2011, Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring.

[8]  H. Shea,et al.  Fabrication Process of Silicone-based Dielectric Elastomer Actuators , 2016, Journal of visualized experiments : JoVE.

[9]  W. Yuan,et al.  Fault‐Tolerant Dielectric Elastomer Actuators using Single‐Walled Carbon Nanotube Electrodes , 2008 .

[10]  Ron Pelrine,et al.  Standards for dielectric elastomer transducers , 2015 .

[11]  Z. Suo,et al.  Mechanisms of Large Actuation Strain in Dielectric Elastomers , 2011 .

[12]  Istvan Denes,et al.  Ageing of Silicone-Based Dielectric Elastomers Prepared with Varying Stoichiometric Imbalance: Changes in Network Structure, Mechanical, and Electrical Properties , 2016 .

[13]  Q. Pei,et al.  High-speed electrically actuated elastomers with strain greater than 100% , 2000, Science.

[14]  Chauncey Graetzel,et al.  Reducing laser speckle with electroactive polymer actuators , 2015, Smart Structures.

[15]  Samuel Rosset,et al.  An instrument to obtain the correct biaxial hyperelastic parameters of silicones for accurate DEA modelling , 2014, Smart Structures.

[16]  Todd A. Gisby,et al.  Multi-functional dielectric elastomer artificial muscles for soft and smart machines , 2012 .

[17]  Alexandre Poulin,et al.  Dielectric elastomer actuator for mechanical loading of 2D cell cultures. , 2016, Lab on a chip.

[18]  Stefan Seelecke,et al.  Development of a fatigue testing setup for dielectric elastomer membrane actuators , 2017, Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring.

[19]  H. Shea,et al.  Flexible and stretchable electrodes for dielectric elastomer actuators , 2012, Applied Physics A.

[20]  C. Keplinger,et al.  Harnessing snap-through instability in soft dielectrics to achieve giant voltage-triggered deformation , 2012 .

[21]  Alexandre Poulin,et al.  Printing low-voltage dielectric elastomer actuators , 2015 .

[22]  Guillaume Ardoise,et al.  Standing wave tube electro active polymer wave energy converter , 2012, Smart Structures.

[23]  Bert Müller,et al.  Siloxane-based thin films for biomimetic low-voltage dielectric actuators , 2015 .

[24]  Emilio Calius,et al.  Integrated extension sensor based on resistance and voltage measurement for a dielectric elastomer , 2007, SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring.

[25]  Samuel Rosset,et al.  Dielectric elastomer generators that stack up , 2014 .

[26]  F. Carpi,et al.  Ultrafast all-polymer electrically tuneable silicone lenses , 2016 .

[28]  Qibing Pei,et al.  Long lifetime, fault-tolerant freestanding actuators based on a silicone dielectric elastomer and self-clearing carbon nanotube compliant electrodes , 2013 .

[29]  Samuel Rosset,et al.  Small, fast, and tough: Shrinking down integrated elastomer transducers , 2016 .

[30]  Choon Chiang Foo,et al.  Giant, voltage-actuated deformation of a dielectric elastomer under dead load , 2012 .

[31]  R. Pelrine,et al.  Electrostriction of polymer dielectrics with compliant electrodes as a means of actuation , 1998 .

[32]  Samuel Rosset,et al.  Maximizing the displacement of compact planar dielectric elastomer actuators , 2015 .

[33]  P. Dubois,et al.  Metal Ion Implantation for the Fabrication of Stretchable Electrodes on Elastomers , 2009 .

[34]  G. Kovács,et al.  Dielectric elastomer actuators used for pneumatic valve technology , 2013 .