Conjugated polymer actuators provide delicate solutions in biomimetic robotics and bio/micromanipulation. For these
applications, it is highly desirable to have large deformation. Because linear elasticity theory is only valid when the
strain is small, this poses significant challenges in the electromechanical modeling. In this paper, we use a nonlinear
strain energy function to capture the stored elastic energy under actuation-induced swelling, which further allows us to
compute the induced stress. Numerical method is used to obtain the deformation variables by solving the force and
bending moment balance equations simultaneously. Experimental results for a trilayer conjugated polymer beam can be
predicted by the proposed model better than the linear model. This proposed framework can also be applied to the analysis
of large deformations of other electroactive polymers.
In this paper the behavior of conjugated polymers as mechanical sensors is experimentally characterized and modeled. A
trilayer conjugated polymer sensor is considered, where two polypyrrole (PPy) layers sandwich an amorphous polyvinylidene
fluoride (PVDF) layer, with the latter serving as an electrolyte tank. A theory for the sensing mechanism is proposed
by postulating that, through its influence on the pore structure, mechanical deformation correlates directly to the concentration
of ions at the PPy/PVDF interface. This provides a key boundary condition for the partial differential equation (PDE)
governing the ion diffusion and migration dynamics. By ignoring the migration term in the PDE, an analytical model is
obtained in the form of a transfer function that relates the open-circuit sensing voltage to the mechanical input. The model
is validated in experiments using dynamic mechanical stimuli up to 50 Hz.
The reduction-oxidation (redox) level of a conjugated polymer has significant impact on its electro-chemo-mechanical
properties, such as conductivity, impedance, and Young's modulus. A redox level-dependent impedance model is developed
in this paper by including the dynamics of ion diffusion, ion migration, and redox reactions. The model, in the form
of a transfer function, is derived through perturbation analysis around a given redox level. Experimental measurements
conducted under different redox conditions correlate well with the model prediction and thus validate the proposed model.
This work, for the first time, incorporates the effect of redox level into the dynamics of conjugated polymers, and facilitates
the future use of nonlinear control methods for the effective control of these materials.
Conjugated polymers are promising actuation materials for bio and micromanipulation systems, biomimetic
robots, and biomedical devices. Sophisticated electrochemomechanical dynamics in these materials, however,
poses significant challenges in ensuring their consistent, robust performance in applications. In this paper an
effective adaptive control strategy is proposed for conjugated polymer actuators. A self-tuning regulator is
designed based on a simple actuator model, which is obtained through reduction of an infinite-dimensional
physical model and captures the essential actuation dynamics. The control scheme is made robust against
unmodeled dynamics and measurement noises with parameter projection, which forces the parameter estimates to
stay within physically-meaningful regions. The robust adaptive control method is applied to a trilayer polypyrrole
actuator that demonstrates significant time-varying actuation behavior in air due to the solvent evaporation.
Experimental results show that, during four-hour continuous operation, the proposed scheme delivers consistent
tracking performance with the normalized tracking error decreasing from 11% to 7%, while the error increases
from 7% to 28% and to 50% under a PID controller and a fixed model-following controller, respectively. In the
mean time the control effort under the robust adaptive control scheme is much less than that under PID, which
is important for prolonging the lifetime of the actuator.
Conjugated polymers have promising applications as actuators in biomimetic robotics and bio/micromanipulation.
For these applications, it is highly desirable to have predictive models available for feasibility study and design
optimization. In this paper a geometrically-scalable model is presented for trilayer conjugated polymer actuators
based on the diffusive-elastic-metal model. The proposed model characterizes actuation behaviors in terms of
intrinsic material parameters and actuator dimensions. Experiments are conducted on polypyrrole actuators of
different dimensions to validate the developed scaling laws for the quasi-static force and displacement output,
the electrical admittance, and the dynamic displacement response.