This document is downloaded from DR‑NTU (https://dr.ntu.edu.sg) Nanyang Technological University, Singapore. Novel material composites for dielectric elastomer actuators Ankit 2019 Ankit. (2019). Novel material composites for dielectric elastomer actuators. Doctoral thesis, Nanyang Technological University, Singapore. https://hdl.handle.net/10356/136574 https://doi.org/10.32657/10356/136574 This work is licensed under a Creative Commons Attribution‑NonCommercial 4.0 International License (CC BY‑NC 4.0). Downloaded on 08 Oct 2021 03:29:50 SGT NOVEL MATERIAL COMPOSITES FOR DIELECTRIC ELASTOMER ACTUATORS ANKIT SCHOOL OF MATERIALS SCIENCE AND ENGINEERING 2019 NOVEL MATERIAL COMPOSITES FOR DIELECTRIC ELASTOMER ACTUATORS ANKIT SCHOOL OF MATERIALS SCIENCE AND ENGINEERING A thesis submitted to the Nanyang Technological University in partial fulfilment of the requirement for the degree of Doctor of Philosophy 2019 Statement of Originality I hereby certify that the work embodied in this thesis is the result of original research, is free of plagiarised materials, and has not been submitted for a higher degree to any other University or Institution. 22nd July 2019 . Date Ankit Supervisor Declaration Statement I have reviewed the content and presentation style of this thesis and declare it is free of plagiarism and of sufficient grammatical clarity to be examined. To the best of my knowledge, the research and writing are those of the candidate except as acknowledged in the Author Attribution Statement. I confirm that the investigations were conducted in accord with the ethics policies and integrity standards of Nanyang Technological University and that the research data are presented honestly and without prejudice. 22nd July 2019 . Date Assoc Prof Nripan Mathews Authorship Attribution Statement This thesis contains material from 3 paper(s) published in the following peer-reviewed journal(s) / from papers accepted at conferences in which I am listed as an author. Portions of Chapter 4 are published as Ankit, N. Tiwari, M. Rajput, N. A. Chien, N. Mathews. Highly Transparent and Integrable Surface Texture Change Device for Localized Tactile Feedback. Small 14, 1702312 (2018). DOI: 10.1002/smll.201702312. The contributions of the co-authors are as follows: • I conceived the idea with guidance from Prof N. Mathews and performed all the laboratory work and analysis at the School of Materials Science and Engineering, NTU. • N. Tiwari performed the UV-Vis measurements for the samples. • M. Rajput helped with the spray coating of silver nanowires for initial samples and process optimization. • I prepared the manuscript drafts and the manuscript was revised by Dr N. A. Chien and Prof N. Mathews. Chapter 5 is currently being prepared as a manuscript – Ankit, F. Ho, N. Tiwari, F. Krisnadi, S. J. A. Koh, N. Mathews. Bioinspired liquid filler based soft elastomeric composites for electrically powered soft actuators. The contributions of the co-authors are as follows: • I conceived the idea with guidance from Prof N. Mathews and performed all the laboratory work and analysis at the School of Materials Science and Engineering, NTU. • F. Ho. prepared the initial samples for proof of concept experiments. • N. Tiwari helped with the Fourier transform infrared spectroscopy. • F. Krisnadi prepared the schematic sketches for the manuscript. • Prof S. J. A. Koh at Department of Mechanical Engineering (NUS) helped with the dielectric spectroscopy measurements. • I prepared the manuscript drafts and the manuscript was revised by F. Krisnadi, Prof S. J. A. Koh and Prof N. Mathews. Chapter 6 is published as Ankit, N. Tiwari, M. Rajput, N. A. Chien, N. Mathews. Highly Transparent and Integrable Surface Texture Change Device for Localized Tactile Feedback. Small 14, 1702312 (2018). DOI: 10.1002/smll.201702312. Portions of Chapter 6 are published as Ankit, J. Y. Chan, L. L. Nguyen, F. Krisnadi, N. Mathews. Large-area, flexible, integrable and transparent DEAs for haptics. Proc. SPIE 10966, Electroactive Polymer Actuators and Devices (EAPAD) XXI, 109661W (13 March 2019). DOI: 10.1117/12.2514267. The contributions of the co-authors are as follows: • I conceived the idea with guidance from Prof N. Mathews and performed all the laboratory work and analysis at the School of Materials Science and Engineering, NTU. • J. Y. Chan carried out the device integration with Arduino and capturing the images. • L. L. Nguyen performed the synthesis of conductive hydrogels. • I prepared the manuscript drafts and the manuscript was revised by J. Y. Chan, L. L. Nguyen and Prof N. Mathews. Portions of Chapter 6 are also published as Ankit, N. A. Chien, N. Mathews. Surface texture change on-demand and microfluidic devices based on thickness mode actuation of dielectric elastomer actuators (DEAs). Proc. SPIE 10163, Electroactive Polymer Actuators and Devices (EAPAD) 2017, 101632G (17 April 2017). DOI: 10.1117/12.2260300. The contributions of the co-authors are as follows: • I conceived the idea with guidance from Prof N. Mathews and performed all the laboratory work and analysis at the School of Materials Science and Engineering, NTU. • I prepared the manuscript drafts and the manuscript was revised by N. A. Chien and Prof N. Mathews. Chapter 7 is currently being prepared as a manuscript – Ankit, F. Krisnadi, D. Accoto, S. J. A. Koh, N. Mathews. Thermally activated reversible rigidity composites for next generation soft actuators. The contributions of the co-authors are as follows: • I conceived the idea with guidance from Prof N. Mathews and performed all the laboratory work and analysis at the School of Materials Science and Engineering, NTU. • F. Krisnadi helped with sample preparations and sample characterizations. F. Krisnadi also prepared the schematic sketches for the manuscript. • Prof D. Accoto at School of Mechanical and Aerospace Engineering (NTU) helped with the analysis of data from mechanical characterizations. • Prof S. J. A. Koh at Department of Mechanical Engineering (NUS) helped with the dielectric spectroscopy measurements. • I prepared the manuscript drafts and the manuscript was revised by F. Krisnadi, Prof D. Accoto, Prof S. J. A. Koh and Prof N. Mathews. 22nd July 2019 . Date Ankit Abstract Abstract Conventional robotics, made from rigid components, are known for their accuracy and precision, and have been extensively utilized in industries for large scale manufacturing. There has been a constant focus to improve the existing robots and make them fit in our natural world, leading to the development of modern era humanoids and animal-inspired robots. However, they suffer from the absence of compliance and do not provide a safe and comfortable environment for human interaction. On the other hand, biological systems make use of their inherent softness and structural compliance to produce complex and fluidic motions. An emerging area of research, soft robotics, promises to address these issues of rigidity and non-dexterity in conventional robots and mimic the systems found in nature. They make use of soft materials and demonstrate fluidic deformation of their bodies to achieve more complex and compliant motions. Different strategies like embedded pneumatics and fluidics, thermally activated polymers, magnetic fields, chemical reactions and electroactive polymers have been adopted for actuating these soft materials. Dielectric elastomer actuators, under the family of electroactive polymers are an attractive option for producing actuation, and they utilize electric fields to deform elastomers and can produce very large actuation strains. However, in their current form, dielectric elastomer actuators suffer from specific limitations like high electric fields, low versatility and need for rigid frames, which calls for investigation into new material systems and novel device configurations. This dissertation attempts to tackle the material and device configuration issues with these field driven soft actuators. The performance of dielectric elastomer actuators is dependent on intrinsic material properties like dielectric constant and Young’s modulus of the elastomer. Commonly used elastomeric systems suffer from low dielectric constant and comparatively high Young’s modulus. Conventional approaches to improve these material properties involve chemical modification of the elastomeric backbone and addition of solid fillers, often producing undesirable effect on other material parameters. Drawing inspiration from biological materials like skin and tissues, it is hypothesized that addition of a high dielectric constant liquid filler into a polymer matrix with favorable compatibility, could lead to significant reduction in mechanical stiffness accompanied with the i Abstract improvement in the dielectric constant of the resulting composite. Theoretical models are adopted to predict the properties of such a self-contained liquid filler-polymer composite. Ionic liquid and water are investigated as liquid fillers and the role of their interaction with the polymer on the resulting composite is established. Owing to their favorable interaction and other desirable properties, ionic liquid is chosen as the suitable filler, and they produce synergetic effects on the electrical and mechanical properties of the resulting composite. Benchmarking of the actuation behavior against the conventional elastomeric matrix reveals a considerable improvement in the electromechanical performance at significantly low electric fields. Owing to the suitable choice of filler and adoption of a liquid-solid