Project Title: Energy harvesting by dielectric elastomer generators

1. Project Title:Energy harvesting by dielectric elastomer generators Project Number: IZERZO_142215/1, NR:10/RO-CH/RSRP/01.01.2013 Funding organisms: RSRP 2011 – 2016: Romanian-Swiss Research Programme SNSF and UEFISCDI Swiss PI:Dr. Dorina Maria Opris, Empa, Dübendorf Romanian PI:Dr. Carmen Racles, “P. Poni” Institute of Macromolecular Chemistry, Iasi

2. 1. Summary The search for new reliable green sources of energy increased significantly in the last years. Nature offers a number of sources of “unlimited” energy, ocean wave’s energy being one of them. Dielectric elastomer generators (DEGs) are a relatively new technology that can convert mechanical energy (e.g. wave energy) into more useful electrical energy. DEGs consist of a thin elastic film coated on both sides with compliant and stretchable electrodes (a stretchable capacitor). When such device is strained by an external force, charged in this strained form and let contract by the elastic restoring forces, the like charges on the electrodes are squeezed together while the distance between the unlike charges is increased. These results in an increase of the voltage of the charge and thus mechanical energy can be converted into electrical energy. Unfortunately, the existing materials have insufficient performance which limits the application potential of this technology. It is the aim of this project to develop new materials for DEG. Dielectric materials with good elastic properties, low viscoelastic losses, high strain at break, increased dielectric constant (ε’), low dielectric losses, and high breakdown fields are the target.

3. We focused on silicones due to their suitable mechanical properties over a wide frequency and temperature range. Additionally, they not only allow chemical modification and functionalization of the polymer chain with functional groups but also the selection of appropriate crosslinking reactions for thin film formation. New silicone based elastomeric materials with increased dielectric constant, low dielectric losses, low conductivity, and good mechanical properties will be prepared. In order to increase the dielectric constant, polar groups will be attached to the silicone chains. Small polar groups like CN and CF3 as well as molecules with larger dipole moments are attractive. Copolymers containing different amounts of dipoles at random position on the chain as well as copolymers where the position of the dipole is precisely controlled will be made in the project. The influence of the amount and type of the dipole, their position on the polymer chain, molecular weight, crosslinking density on the dielectric and electromechanical properties will be investigated. Unfortunately silicones have poor strain at break and therefore have to be reinforced. Two different approaches will be followed for the reinforcement. First, filler particles will be used and the amount of filler will be optimized to meet the requirements for generator applications. In a second approach, strain induced crystallization of designed silicones will be used to reinforce the elastomer. It is expected that by using this type of reinforcement high breakdown field elastomers can be prepared. The newly prepared materials will be investigated regarding their mechanical and electrical properties as well as regarding their feasibility to convert mechanical energy into electrical energy. At the end of the project, not only should a good material for DEG be achieved but also the understanding on structure property relationship will be greatly improved.

4. 2. Budget

5. 3. RESULTS 2013 Published papers: “Synthesis and characterization of silicones containing cyanopropyl groups and their use in dielectric elastomer actuators”, Carmen Racles, Maria Cazacu, Beatrice Fischer, Dorina M Opris; Smart Mater. Struct. 22 (2013) 104004 Papers under review: 1. “Tuning the electromechanical properties of silicones by crosslinking agent”, Maria Cazacu, Adrian Bele, Carmen Racles, Dorina M. Opris, George Stiubianu, Dragos Ovezea, Mircea Ignat; 2. “Tailoring the dielectric properties of silicones by chemical modification”, Carmen Racles, Mihaela Alexandru, Adrian Bele, Valentina Musteata, Maria Cazacu, Dorina Opris – book chapter: “Research Developments in Polymer Science” Research Signpost, Transworld Research Network.

6. Communications: • “Silicone elastomers for actuation” (poster), Carmen Racles, Maria Cazacu, Dorina Opris- EuroEAP 2011: First international conference on Electromechanically Active Polymer (EAP) transducers & artificial muscles, 8 – 9 June 2011, Pisa, Italy; • "Dielectric elastomers put to work", D. M. Opris, S. Dünki, F. Nüesch, J. E. Q. Quinsaat, Y. Song Ko, S. Michel, C. Racles, M. Cazacu, SCS Fall Meeting 2013, 6 September 2013, Lausanne, Switzerland; • "Self-reparable Dielectric Elastomer Actuators", Dorina M. Opris, Sascha Grimm, Frank Nüesch, Martin Molberg, Gabor Kovacs, Carmen Racles, Maria Cazacu, Jose Quinsaat, Heinrich Hofmann, Makromolekulares Kolloquium Freiburg, 23 – 25 February 2012, Freiburg, Germany; • "Dielectric elastomer actuators", Dorina M. Opris, Jose Enrico Q. Quinsaat, Frank Nüesch, Heinrich Hofmann, Carmen Racles, Maria Cazacu, Makromolekulares Kolloquium Freiburg, 24 – 26 February 2013, Freiburg, Germany; • “Effect of crosslinking agents on the electromechanical properties of silicones” (poster), Adrian Bele, Maria Cazacu, Carmen Racles, Dorina M. Opris, Mircea Ignat, George Stiubianu, Valentina Musteata, EuroEAP 2013: International conference on Electromechanically Active Polymer (EAP) transducers & artificial muscles, 25 – 26 June 2013, Dübendorf, Switzerland;

7. Communications: 6. “Synthesis and characterization of silicones containing cyanopropyl groups and their use in dielectric elastomer actuators” (poster), Carmen Racles, Maria Cazacu, Beatrice Fischer, Dorina M Opris, EuroEAP 2013: International conference on Electromechanically Active Polymer (EAP) transducers & artificial muscles, 25 – 26 June 2013, Dübendorf, Switzerland; 7. “Tailoring the dielectric properties of silicones by chemical modification” (poster), Carmen Racles, Mihaela Alexandru, Valentina Musteata, Adrian Bele, Maria Cazacu, 4 – 6 July 2013, The 13th International Balkan Workshop on Applied Physics, Constanta, Romania; 8. “Silicone polymers with polar groups designed for actuation” (poster), Carmen Racles, Maria Cazacu, Mihaela Alexandru, Adrian Bele, Valentina Musteata, Daniela Ionita, Stelian Vlad, Cristian Varganici, Florica Doroftei, 2 – 5 October 2013, Zilele Academice Iesene, Iasi, Romania;