PURSE 1999

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https://ir.lib.pdn.ac.lk/handle/20.500.14444/47

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Browsing PURSE 1999 by Author "Dissanayake, M. A. K. L."

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    Artificial Muscles with a Polymer Gel Electrolyte Based on Polyacryonitrile (Pan)
    (Unviersity of Peradeniya, Peradeniya, Sri Lanka, 1999-11-20) West, Keld; Skaarup, Steen; Bandaranayake, P. W. S. K.; Perera, Kumudu; Dissanayake, M. A. K. L.
    Polymer gel electrolytes are formed by trapping a liquid electrolyte in a polymer matrix. They offer an approach to achieve high conductivity nearing that of the parent liquid electrolyte alongside good mechanical properties. Polymer networks found to be useful to form gel electrolytes include poly(acrylonitrile)(PAN), poly(methyl methacrylate) (PMMA), poly(vinyl chloride) (PVC) and poly(vinylidene fluoride) (PVDF). They have exhibited their potential capability in various applications. The most latest application of these gel electrolytes is in the artificial muscles which are defined as systems capable of converting chemical energy to mechanical energy. Different types of materials have been tested in artificial muscles. But, due to their practical difficulties such as requirement of high voltages and low displacements, the attention has diverted towards conducting polymers. Most studies have been done with conducting polymer based artificial muscles in liquid electrolytes. Recently, a keen interest has been put on dry artificial muscles where liquid electrolyte is replaced by a polymer electrolyte. Upon application of a potential, movements are registered as in a liquid electrolyte. This report is based on a gel eletrolyte comprising PAN, ethylene carbonate (EC), propylene carbonate (PC) and lithium trifluoromethane sulfonate (LiCF3S03) and its performance on artificial muscles prepared with conducting polymer polypyrrole (PPy). The composition having the maximum room temeprature condcivity and the optimum mechanical properties was determined by varying the salt concentration and the PAN amount respectively. It was found that the highest room temperature can be obtained at the salt concentration 0.87 molkg-1 and good mechanical properties are available with a PAN amount corresponding to 1/10 of the amount of the liquid electrolyte (by weight). The highest room temeprature conductivity was 1.21 x 10-3 S cm-1 and the electrolyte composition was 15mol%PAN : 42mol%EC : 36mol%PC : 7mol%LiCF3S03. To fabricate the artificial muscle, two identical polypyrrole electrodes polymerized in the presence of sodium dodecylbenzene sulfonate (SOBS) and having thicknesses of 10 µm were used. The gel electrolyte was sandwiched in between two PPy electrodes. Movements were observed in different potential windows. To accelerate the motion, gel electrolytes of different thicknesses were used. It could be noticed that thinner the gel electrolyte, faster the movements. But, using very thin electrolytes sometimes resulted short circuit effects. There are problems like evaporation of the solvents. Further studies are under way to overcome them.
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    Bilayer Actuators(Artificial Muscles) Based on Polypyrrole
    (Unviersity of Peradeniya, Peradeniya, Sri Lanka, 1999-11-20) Vidanapathirana, K. P.; Careem, M. A.; Dissanayake, M. A. K. L.; Skaarup, Steen; West, Keld
    Various conducting polymers, including polypyrrole (PPy), undergo significant dimensional changes upon electrochemical doping (oxidation) and dedoping (reduction). These changes are linked with the movement of ions and solvents in and out of the polymer during those processes. The conformational changes occurring here are reversible and it has been suggested that this behaviour can be applied in a range of devices such as electrochemically driven mechanical actuators (artificial muscles), micro-structures. These artificial muscles are termed as electrochemomechanical actuators since they work with electric pulse which generate the electrochemical reaction ultimately converted into mechanical energy. In this work, we report about the fabrication of a bilayer artificial muscle with conducting polymer as active layer and a non-conducting polymer as the passive layer. Force measurements were done using the bending beam method, which was used to study the volume changes in the conducting polymer phase in bilayers. Preparation of the artificial muscle was done by electrochemically polymerizing a pyrrole film on a 25µm thick polyimide film ( size 20 x 5 mm) which was coated with 250 Å gold layer to get electrical contacts. Polymerization of pyrrole was done in an aqueous solution containing 0.05 M pyrrole and 0.05 M sodium dodecylbenzenesulfonate (SDBS). Force measurements were done using a microbalance simultaneously with cyclic voltammetry in an aqueous electrolyte of 0.1 M NaCI04. To examine the effect of the film thickness and the polymerization current density on the force, films were prepared with different current densities and with various thicknesses. PPy films were electrochemically deposited on the quartz crystal microbalance electrode to understand the mass change during oxidation and reduction of these films. The force measurement results showed that the films made with higher current densities have larger forces than the films made with lower current densities. They also clearly demonstrated that with the increment of the PPy film thickness, the resultant force showed an increasing trend. When the force. measurements are compared with cyclic voltammetry, it is possible to conclude that the force changes are associated only with main peaks of the cyclic voltammogram. The other interesting feature is that most of the force changes occur in a narrow potential window, which is an advantage in the applications. The results obtained with quartz crystal microbalance showed that during oxidation and reduction 10-20 water molecules co-intercalated to PPy/DBS film with each cation move in and out.