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Electromechanical properties of nanotube–PVA composite actuator bimorphs

Christèle Bartholome1, Alain Derré, Olivier Roubeau, Cécile Zakri and Philippe Poulin1

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Oxidized multiwalled carbon nanotube (oxidized-MWNT)/polyvinyl alcohol (PVA) composite sheets have been prepared for electromechanical actuator applications. MWNT have been oxidized by nitric acid treatments. They were then dispersed in water and mixed with various amounts of PVA of high molecular weight (198 000 g mol−1). The composite sheets were then obtained through a membrane filtration process. The composition of the systems has been optimized to combine suitable mechanical and electrical properties. Thermogravimetric analysis, mechanical tensile tests and conductivity measurements show that the best compromise of mechanical and electrical properties was obtained for a PVA weight fraction of about 30 wt%. In addition, one face of the sheets was coated with gold to increase the conductivity of the sheets and promote uniform actuation. Pseudo-bimorph devices have been realized by subsequently coating the composite sheets with an inert layer of PVA. The devices have been tested electromechanically in a liquid electrolyte (tetrabutylammonium/tetrafluoroborate (TBA/TFB) in acetonitrile) at constant frequency and different applied voltages, from 2 to 10 V. Measurements of the bimorph deflections were used to determine the stress generated by the nanotube–PVA sheets. The results show that the stress generated increases with increasing amplitude of the applied voltage and can reach 1.8 MPa. This value compares well with and even exceeds the stress generated by recently obtained bimorphs made of gold nanoparticles.


PACS

07.07.Tw Servo and control equipment; robots

72.80.Tm Composite materials

62.25.-g Mechanical properties of nanoscale systems

81.70.Pg Thermal analysis, differential thermal analysis (DTA), differential thermogravimetric analysis

73.63.-b Electronic transport in nanoscale materials and structures

81.16.-c Methods of nanofabrication and processing

Subjects

Condensed matter: electrical, magnetic and optical

Instrumentation and measurement

Condensed matter: structural, mechanical & thermal

Nanoscale science and low-D systems

Dates

Issue 32 (13 August 2008)

Received 12 February 2008, in final form 16 June 2008

Published 2 July 2008



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