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Actuators based on carbon nanotubes (CNT) have the potential to generate high forces at very low voltages. The
density of the raw material is just 1330 kg/m3, which makes them well applicable for lightweight applications.
Moreover, active strains of up to 1% can be achieved - due to the CNTs dimensional changes on charge injection.
Therefore the nanotubes have to be arranged and electrically wired like electrodes of a capacitor. In previous
works the system's response of the Nanotubes comprising a liquid electrolyte was studied in detail. The major
challenge is to repeat such experiments with solid electrolytes, which is a prerequisite for structural integration.
In this paper a method is proposed which makes sure the expansion is not based on thermal expansion. This
is done by analysing the electrical system response. As thermal expansion is dominated by ohmic resistance the
CNT based actuators show a strong capacitive behavior. This behavior is referable to the constitution of the
electrochemical double layer around the nanotubes, which causes the tubes to expand. Also a novel test setup is
described, which guarantees that the displacement which is measured will not be caused by bending of a bimorph
but due to expansion of a single layer of nanotubes. This paper also presents experimental results demonstrating
both, the method of electrical characterization of CNT based actuators with implemented solid electrolytes
and the novel test setup which is used to measure the needed data. The actuators which were characterized
are hybrids of CNT and the solid electrolyte NAFION which is supplying the ions needed to constitute the
electrochemical double layer. The manufacturing, processing of these actuators and also some first experimental
results are shown. Unfortunately, the results are not as clear as those for liquid electrolytes, which depend on
the hybrid character of the analyzed devices. In the liquid electrolyte based case the CNTs are the only source
of stiffness, whereas in the solid electrolyte case electrodes and electrolyte contribute to the overall stiffness and
damping as well. Since the introduction of solid electrolytes is a major stumbling block in the development of
such actuators, this work is of particular importance.
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