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Characterization of IPMCs by impedance spectroscopy in controlled environment and temperature

Grant number: 17/13521-0
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): September 01, 2017
Effective date (End): January 31, 2018
Field of knowledge:Engineering - Materials and Metallurgical Engineering
Principal Investigator:Carlos Henrique Scuracchio
Grantee:Rean Toniazzo
Home Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil

Abstract

iEAPs have been studied in recent decades as a new approach for electromechanical actuators in medicine and robotics. This is due to the ability of these materials to generate silent, light and precise movements with great displacement from small electrical stimuli (on the order of 1V). In addition, they have remarkable properties for such applications as low density, low cost, simple construction, weather resistance, easy miniaturization and low energy consumption. The movement generated by this type of material occurs because of the migration of mobile ionic species in their volume when subjected to an electric field. If all mobile ions have the same charge, they will move in the same direction, expanding the iEAP on one side, in the direction of the displacement. The charges of these ions will dictate the direction of the displacement. On the other hand, the opposing ions will not dislocate because they are attached to the polymeric structure, such as, for example, sulfonated groups. The expansion of only one side generates a fold in the structure, which defines the movement of the material. Polymer-metal ionic composites (IPMCs) consist of a membrane of an iEAP (180-200 ¼m) between extremely thin metal plates (5-10¼m), usually consisting of noble metals such as platinum or silver, which act as electrodes. The most widely used iEAPs for this type of application are those having a hydrophobic main chain (made up of, for example, PTFE), and short branching with hydrophilic ionic groups, such as sulfonated ethers. Although more than one material fits into this category, the most commonly used is Nafion. Through several studies it is notable that the performance of Nafion is directly influenced by several factors, such as temperature, relative humidity and the counterions present in the membrane. In order to expand the possible applications of these devices, a clear understanding, both quantitative and qualitative, of each of these variables is necessary. The expected contribution of this research project is a better understanding of the mechanisms of ionic transport and the influence of temperature, hydration degree and size of the mobile ion (contraction) in the development of these mechanisms. For this, the impedance spectroscopy technique in controlled humidity and with different size counterions will be used. (AU)