Single-Walled Carbon Nanotubes — Ionic Polymer Electroactive Hybrid Transducers

Abstract

Ionic electroactive polymers, sometimes referred to as artificial muscles, have the ability to generate large bending strain and moderate stress at low applied voltages. Typical types of ionic electroactive polymer transducers include ionic polymers, conducting polymers, and carbon nanotubes. Preliminary research combining multiple types of materials proved to enhance certain transduction properties. Bennett and Leo (Materials Research Society Symposium Proceedings, vol. 785, 2003b) showed that the speed of response, maximum strain, and quasi-static actuation are improved by adding a layer of conducting polymer on an ionic polymer transducer. In this work, a recently developed fabrication method called the direct assembly process (DAP) plating is used to build SWNT/RuO 2 hybrid transducers. The DAP consists of mixing a conducting powder with an ionomer solution. This technique has demonstrated improved response time and strain output as compared to previous methods. Electrodes applied using this new technique of mixing RuO 2 (surface area 45-65 m 2 =g) particles and Nafion TM dispersion provided 5Â the displacement and 10Â the force compared to a transducer made with conventional methods. Furthermore, previous studies demonstrated that the response speed of the transducer is optimized by varying the composition of metal in the electrode (Akle, B.. 2007. ''Direct Assembly Process: A Novel Fabrication Technique for Large Strain Ionic Polymer Transducers,'' Journal of Mat. Sci., 42:7031-7041). For RuO 2 , the optimal loading was approximately 45 vol%, while carbon nanotubes electrodes have an optimal performance at 30 vol%. Due to low percolation threshold, carbon nanotubes actuators perform better at a lower loading compared to other conducting powders. The addition of single-walled carbon nanotubes (SWNT) to the electrode increases both the strain rate and the maximum strain of the hybrid actuator. The strain rate of the transducer increased proportional to the ratio of SWNT to RuO 2 in the electrode. A maximum peak-to-peak strain of 10.6% (AE2 V) is attained in a 15 vol% SWNT/30 vol% RuO 2 hybrid transducer. The maximum strain rate of 2.7%/s is generated by a 20 vol% SWNT/25 vol% RuO 2 hybrid transducer.

High surface area electrodes in ionic polymer transducers: Numerical and experimental investigations of the electro-chemical behavior

“…In comparison to other types of materials that exhibit electro-mechanical coupling, such as piezoelectric materials, ionomeric materials have been shown to produce bending strains on the order of 5% under the application of potentials of less than 4 V (Ref. 5). Recent advances in the development of 'dry' materials have also enabled the use of these ionomeric materials in air, 6,7 thus increasing the practicality of using these materials in environments that do not require control over hydration or humidity.…”

High temperature polymer capacitors for aerospace applications

“…An electric double layer is defined as a region at the boundary of two substances, with dimensions at a molecular scale, containing charged particle (e.g. ions) across which an electrical field exists due to the separation of electrical charges (10). The electrostatic attraction between the two separated charges causes an electric field to be established across the interface.…”

Development of ionic polymer transducers as flow shear stress sensors: effects of electrode architecture

“…The strain rate is a function of the loading and conductivity of the conductor particulate in the electrode. Moreover, this novel method enables improved IPT actuation performance by a factor of 50x, resulting in strains of over 10% [14]. This method also allows patterning of the electrode using micro lithography techniques, resulting in distributed sensing and/or energy harvesting.…”