Figure 1 - Polypyrrole based micro-actuators
Figure 1 - Polypyrrole based micro-actuators
Conducting polymers can be used as electro-mechanical actuator materials. The actuation mechanism in the case of redox polymers
is based on the migration of ions in and out of the polymer during redox cycling. Among other polymers, polypyrrole (PPy) doped
with anions can be used as an actuatos. Polypyrrole actuators in particular can be structured and fabricated with standard
lithography and thin film structuring methods. PPy based actuators operate at low voltages (1 V or less), PPy is biocompatible,
and operates ideally in liquid electrolytes (including biofluids).
PPy based micro-actuators consists of a polypyrrole/gold (PPy/Au) bilayer structure. Simple mechanical models can not predict the
resulting bending angle behavior or resulting forces of these bilayers. Therefore, experimental data are needed to develop models
that correctly forecast the performance of these PPy/Au bilayers. They should predict that there is a ratio of PPy to Au thicknesses
at which bending angle is maximum, whereas force simply increases with PPy thickness. This information is need for any real application
of polypyrrole/gold bilayer actuators. We studied systematically the resulting bending of PPy/Au bilayers. Starting with predictions
from existing models, ranges of PPy and Au thicknesses and hinge lengths were chosen to be investigated, and samples were fabricated
that varied these parameters independently. Bending angles were recorded. Beside the bending behaivor we studied the resulting forces
and response times of these actuators to generate a comprehensive experimental characterization. We measured the isometric forces
exerted by the hinges with a mciro-force transducer. The response times of the PPy based actuators were directly measured with machine
vision tools.