The Role of Macroscopic Defects on Electromechanical Instability in Elastomer Dielectrics and Strategies for Mitigation

Purdue University, West Lafayette IN

Investigators

Abstract

Polymer-based actuators provide new opportunities for emerging fields such as human machine interfaces due to their low cost and mechanical flexibility. Electrical actuation of soft elastomer achieves fast deformation, but the mechanism is limited by susceptibility to defects that can cause elastomer structures to fail prematurely. This award supports fundamental research into the role of defects in electrical actuation of elastomers (i.e, elastomer dielectrics) and explores mechanisms to overcome the negative impact of defects. The insights from this work could enable the adoption of low-cost polymer actuators for applications in medical devices, consumer electronics, and national defense, thus contributing to the benefit of society. The interdisciplinary nature of the work, spanning materials properties, mechanics of structures, and electronic properties, provides training opportunities for students in an emerging high-tech field. The award includes activities that leverage excitement about 3D printing and soft robotics to recruit students towards research. At the high school level, the award supports a course on 3D printing that includes content on the mechanics of polymers and their impact on the strength of structures. At the undergraduate level, a soft robotics club offers students the opportunity to get hands-on experience with the effect of polymer mechanics on robot performance. Electromechanical instability has been characterized for idealized elastomer dielectrics in a wide range of geometries. However, in manufactured systems, defects can reduce the critical electric field, which leads to the onset of instability, limiting the capability of the structure. The electromechanical deformation of many defects cannot be modeled analytically, motivating the use of a finite element approach. In this research, a finite element model will be validated through experimental monitoring of the electrically induced deformation in single-layer dielectrics with controlled sizes of defects. These devices will consist of silicone dielectrics to minimize non-idealities associated with viscoelasticity and dielectric dispersion. Finite element modeling over a range of defect sizes and geometries will provide computationally derived trends in the free energy associated with defects as a function of the defect size, geometry, and constitutive model of the elastomer. Multilayer dielectrics will be modeled to determine the influence of defects within one component of mechanically coupled structures. The introduction of discontinuous stiff electrodes in multilayer dielectrics will be investigated computationally and experimentally as a method to mitigate the effect of defects. Knowledge gained in this work will provide insights into the role of defects in field-coupled deformable structures. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.