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In this paper, we analytically and experimentally study the energy harvesting capability of submerged ionic polymer metal composites (IPMCs). We consider base excitation of an IPMC strip that is shunted with an electric impedance and immersed in a fluid environment. We develop a modeling framework to predict the energy scavenged from the IPMC vibration as a function of the excitation frequency range, the constitutive and geometric properties of the IPMC, and the electric shunting load. The mechanical vibration of the IPMC strip is modeled through Kirchhoff-Love plate theory. The effect of the encompassing fluid on the IPMC vibration is described by using a linearized solution of the Navier-Stokes equations, that is traditionally considered in modeling atomic force microscope cantilevers. The dynamic chemo-electric response of the IPMC is described through the Poisson-Nernst-Planck model, in which the effect of mechanical deformations of the backbone polymer is accounted for. We present a closed-form solution for the current flowing through the IPMC strip as a function of the voltage across its electrodes and its deformation. We use modal analysis to establish a handleable expression for the power harvested from the vibrating IPMC and to optimize the shunting impedance for maximum energy harvesting. We validate theoretical findings through experiments conducted on IPMC strips vibrating in aqueous environments.

In this paper, we analyze the effect of electrode surface roughness on ionic polymer metal composite (IPMC) capacitance. We use the linearized Poisson–Nernst–Planck model to describe the charge and electric potential distribution in response to a small voltage applied across the IPMC electrodes. We use perturbation methods to develop a comprehensive understanding of the interplay among the scale of the electrode roughness, the Debye screening length, and the IPMC nominal dimensions on the electrical behavior of IPMCs. We derive a closed-form expression of the IPMC capacitance per unit nominal surface area in terms of the Debye screening length, the IPMC nominal thickness, and physically relevant statistical properties of the rough landscape. We find that IPMC capacitance is largely dictated by the effective electrode surface area when the Debye screening length is considerably smaller than the polymer thickness. In this case, the diffuse charge layers that form at the polymer-electrode interface closely follow the rough electrodes profile. As the Debye screening length increases, diffuse layers do not completely adhere to the electrode profile, and local curvature changes and additional geometric factors contribute to the overall IPMC capacitance. We specialize our findings to different electrode models, including fractal electrodes that have been recently observed in IPMC morphological studies. We corroborate our theoretical findings with experimental data on the capacitance of in-house fabricated IPMCs.

This paper describes a new three-dimensional (3D) fused filament additive manufacturing (AM) technique in which electroactive polymer filament material is used to build soft active 3D structures, layer by layer. Specifically, the unique actuation and sensing properties of ionic polymer-metal composites (IPMCs) are exploited in 3D printing to create electroactive polymer structures for application in soft robotics and bio-inspired systems. The process begins with extruding a precursor material (non-acid Nafion precursor resin) into a thermoplastic filament for 3D printing. The filament is then used by a custom-designed 3D printer to manufacture the desired soft polymer structures, layer by layer. Since at this stage the 3D-printed samples are not yet electroactive, a chemical functionalization process follows, consisting in hydrolyzing the precursor samples in an aqueous solution of potassium hydroxide and dimethyl sulfoxide. Upon functionalization, metal electrodes are applied on the samples through an electroless plating process, which enables the 3D-printed IPMC structures to be controlled by voltage signals for actuation (or to act as sensors). This innovative AM process is described in detail and the performance of 3D printed IPMC actuators is compared to an IPMC actuator fabricated from commercially available Nafion sheet material. The experimental results show comparable performance between the two types of actuators, demonstrating the potential and feasibility of creating functional 3D-printed IPMCs.

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We study nonlinear vibrations of cantilever beams oscillating in viscous fluids. A handleable expression for the inertial and damping loads due to the encompassing fluid is proposed. We expand on the canonical viscous diffusion theory by incorporating vortex shedding effects at large oscillation amplitudes. Comparison with experimental results on underwater low frequency and large amplitude oscillations of cantilevers is reported. The approach is applicable to the analysis of ionic polymer metal composites vibrating underwater.