Finite element simulation of conducting polymer actuators

Although traditional vibrotactile devices have dominated the global haptic market, they still suffer from poor spatial resolution, poor flexibility, low stretchability, safety issues, and high weight. Emerging electroactive polymer technologies including conducting polymers (CPs) may be suitable to drive thin, compliant haptic devices that can operate at safe and accessible voltages (~ 2 V in the case of conducting polymers). However, optimal sensitivity is achieved at frequencies between 150 and 300 Hz – a frequency range that is difficult to reach in conducting polymers while also producing significant displacement. In this work we develop finite element model that helps explore the trade-off between frequency, displacement, and force, relating these to actuator dimensions and material properties. We developed a finite element analysis (FEA) numerical simulation of CP-based haptic devices, which works based on a combination of the diffusive elastic model (DEM) and modified linear elastic constitutive equations for large deformation. Unlike many previous, analytical models, this simulation paves the way to complete device modeling as it enables geometrically non-linear formulation to be modeled. The novelty of this simulation compared to the previous work is the consideration of the mass and damping effects of the device, which play important roles in describing the resonance frequency response. The model is able to predict frequency responses of tri-layer conducting polymer actuators made from spray coated poly(3,4-ethylenediodythiopehe) polystyrene sulfonate, abbreviated PEDOT:PSS, on poly (vinylidene fluoride) (PVDF) porous membranes. The model employs measured material properties including electronic conductivity, ionic conductivities, elastic modulus, volumetric capacitance, and strain to charge ratio. Frequency responses follow in amplitude from 0.01 to 150 Hz, including through resonance, with some significant differences near resonance. The results extend previous simulation work to include the effects of mass and damping.