Sub-percolative composites for dielectric elastomer actuators

Dielectric elastomer actuators (DEA) based on Maxwell-stress induced deformation are considered for many potential applications where high actuation strain and energy are required. However, the high electric field and voltage required to drive them limits some of the applications. The high driving field could be lowered by developing composite materials with high-electromechanical response. In this study, a sub-percolative approach for increasing the electromechanical response has been investigated. Composites with conductive carbon black (CB) particles introduced into a soft rubber matrix poly-(styrene-co-ethylene-co-butylene-co-styrene) (SEBS) were prepared by a drop-casting method. The resulting composites were characterized by dielectric spectroscopy, tensile tests, and for electric breakdown strength. The results showed a substantial increase of the relative permittivity at low volume percentages, thereby preserving the mechanical properties of the base soft polymer material. Young's modulus was found to increase with content of CB, however, due to the low volume percentages used, the composites still retain relatively low stiffness, as it is required to achieve high actuation strain. A serious drawback of the approach is the large decrease of the composite electric breakdown strength, due to the local enhancement in the electric field, such that breakdown events will occur at a lower macroscopic electric field.

[1]  Ron Pelrine,et al.  Actuation Response of Polyacrylate Dielectric Elastomers , 2001, SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring.

[2]  D. De Rossi,et al.  Silicone–Poly(hexylthiophene) Blends as Elastomers with Enhanced Electromechanical Transduction Properties , 2008 .

[3]  Richard J. Spontak,et al.  Morphological Characteristics of SEBS Thermoplastic Elastomer Gels , 1996 .

[4]  P. Kohl,et al.  Novel polymer–ceramic nanocomposite based on high dielectric constant epoxy formula for embedded capacitor application , 2002 .

[5]  S. Redner,et al.  Introduction To Percolation Theory , 2018 .

[6]  Haisheng Xu,et al.  High-dielectric-constant ceramic-powder polymer composites , 2000 .

[7]  Ce-Wen Nan,et al.  Novel Ferroelectric Polymer Composites with High Dielectric Constants , 2003 .

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

[9]  Helmut F. Schlaak,et al.  Reduction of the Driving Voltage in Dielectric Elastomer Actuators , 2008 .

[10]  Z. Dang,et al.  Carbon nanotube composites with high dielectric constant at low percolation threshold , 2005 .

[11]  D. Rossi,et al.  Dielectric elastomers as electromechanical transducers: Fundamentals, Materials, Devices, Models and Applications of an Emerging Electroactive Polymer Technology , 2008 .

[12]  Zhi-Min Dang,et al.  Dielectric behavior of a metal-polymer composite with low percolation threshold , 2006 .

[13]  Wenjian Weng,et al.  Percolative conductor/polymer composite films with significant dielectric properties , 2007 .

[14]  Guggi Kofod,et al.  The effect of dispersion on the increased relative permittivity of TiO2/SEBS composites , 2009 .

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

[16]  S. Kirkpatrick.  Percolation and Conduction , 1973 .

[17]  Andrew G. Glen,et al.  APPL , 2001 .

[18]  Ji Su,et al.  High-dielectric-constant all-polymer percolative composites , 2003 .

[19]  F. Xia,et al.  An all-organic composite actuator material with a high dielectric constant , 2002, Nature.

[20]  A novel ultra high dielectric constant epoxy silver composite for embedded capacitor application , 2002, 2002 Proceedings. 8th International Advanced Packaging Materials Symposium (Cat. No.02TH8617).

[21]  Z. Suo,et al.  Stretchable gold conductors on elastomeric substrates , 2003 .

[22]  G. Kofod,et al.  Dielectric properties and electric breakdown strength of a subpercolative composite of carbon black in thermoplastic copolymer , 2009 .

[23]  Toshihiro Hirai,et al.  Wrinkled polypyrrole electrode for electroactive polymer actuators , 2002 .

[24]  Yoseph Bar-Cohen,et al.  Electroactive Polymer (EAP) Actuators as Artificial Muscles: Reality, Potential, and Challenges, Second Edition , 2004 .

[25]  Y. Cohen.  Electroactive Polymer (EAP) Actuators as Artificial Muscles - Reality , 2001 .

[26]  Peter Sommer-Larsen,et al.  Silicone dielectric elastomer actuators: Finite-elasticity model of actuation , 2005 .

[27]  D. Rossi,et al.  Dielectric constant enhancement in a silicone elastomer filled with lead magnesium niobate–lead titanate , 2007 .

[28]  Ron Pelrine,et al.  High-Strain Actuator Materials Based on Dielectric Elastomers , 2000 .