Ionic polymer-metal composites (IPMC) are soft actuation materials with promising applications in robotics
and biomedical devices. In this paper, a MEMS-based approach is presented for monolithic, batch fabrication of
IPMC pectoral fin actuators that are capable of complex deformation. Such an actuator consists of multiple, individually
controlled IPMC regions that are mechanically coupled through compliant, passive regions. Prototypes
of artificial pectoral fins have been fabricated with the proposed method, and sophisticated deformation modes,
including bending, twisting, and cupping, have been demonstrated, which shows the promise of the pectoral fin
in robotic fish applications.
Ionic polymer-metal composites (IPMCs) form an important category of electroactive polymers. In this paper,
a nonlinear, physics-based model is proposed for IPMC actuators. A key component in the proposed model
is the nonlinear capacitance of IPMC, demonstrated by the nonlinear relationship between an applied step
voltage and the induced charge. A nonlinear partial differential equation (PDE) is fully considered in analytical
derivation of the capacitance of IPMC. The nonlinear capacitance is incorporated into a circuit model, which
includes additionally the pseudo capacitance, the ion diffusion resistance, and the nonlinear DC resistance of the
polymer. The model is verified in experiments.
In this paper, a model is proposed for a biomimetic robotic fish propelled by an ionic polymer metal composite
(IPMC) actuator with a rigid passive fin at the end. The model incorporates both IPMC actuation dynamics
and the hydrodynamics, and predicts the steady-state speed of the robot under a periodic actuation voltage.
Experimental results have shown that the proposed model can predict the fish motion for different tail dimensions.
Since its parameters are expressed in terms of physical properties and geometric dimensions, the model is expected
to be instrumental in optimal design of the robotic fish.
Ionic polymer-metal composites (IPMCs) have built-in sensing and actuation capabilities which make them attractive in
many biomedical and biological applications. In this paper a physics-based but control-oriented dynamic model is proposed
for IPMC actuators. The modeling work starts from the governing partial differential equation (PDE) that describes the
charge redistribution dynamics under external electrical field, electrostatic interactions, ionic diffusion, and ionic migration
along the thickness direction. It is further extended by incorporating the effect of distributed surface resistance. The
electrical impedance model is obtained by deriving the exact solution to the governing PDE in the Laplace domain. By
assuming a linear electromechanical coupling, an actuation model which relates bending displacement to voltage input
is derived. The model is represented as an infinite-dimensional transfer function, which is amenable to model reduction
and real-time control design while capturing fundamental physics. It thus bridges the traditional gap between the physics-based
perspective and the system-theoretic perspective on modeling of IPMC materials. The model is expressed in terms
of fundamental material parameters and dimensions of the IPMC, and is therefore geometrically scalable. The latter has
been further confirmed in experiments.
Compact sensing schemes are desirable for feedback control of ionic polymer-metal composite (IPMC) actuators
in their targeted bio, micro, and nano applications. In this paper, a novel integrated sensory actuator with both
position and force feedback is designed by combining IPMC with polyvinylidene fluoride (PVDF) films. The
design adopts differential configurations for both the sensor-actuator structure and the sensing circuit, and thus
eliminates capacitive coupling between IPMC and PVDF, minimizes the internal stress at bonding interfaces,
and enables excellent immunity to thermal and electromagnetic noises. Closed-loop position control of the IPMC
output is demonstrated together with simultaneous tip force measurement, based upon the integrated PVDF
position and force sensors.
Compact sensing methods are desirable for ionic polymer-metal composite (IPMC) actuators in microrobotic and biomedical applications. In this paper a novel sensing scheme for IPMC actuators is proposed by integrating an IPMC with a PVDF (polyvinylidene fluoride) thin film. The problem of feedthrough coupling from the actuation signal to the sensing signal, arising from the proximity of IPMC and PVDF, presents a significant challenge in real-time implementation. To reduce the coupling while minimizing the stiffening effect, the thickness of the insulating layer is properly chosen based on the Young's modulus measurement of the IPMC/PVDF structures. Furthermore, a nonlinear circuit model is proposed to capture the dynamics of the still significant coupling effect, and its parameters are identified through a nonlinear fitting process. A compensation scheme based on this model is then implemented to extract the correct sensing signal. Experimental results show that the developed IPMC/PVDF structure, together with the compensation algorithm, can perform effective, simultaneous actuation and sensing. As a first application, the sensori-actuator has been successfully used for the open-loop micro-injection of living Drosophila embryos.