A Brief introduction of the Speaker
Prof. Qing Wang received his Ph.D. in Chemistry from the University of Chicago in 2000. Prior to joining the faculty at Penn State in 2002, he was a postdoctoral researcher at Cornell University. Among other awards, he has received the National Science Foundation CAREER Award, Rustum and Della Roy Innovation in Materials Research Award and Penn State Faculty Scholar Medal in Engineering. His research interests include the development of ferroelectric polymers, electroactive polymers, dielectric polymers and nanocomposites for energy harvesting and storage. Prof. Wang is a Fellow of AAAS and IEEE.
Abstract
Ferroelectric polymers represented by poly(vinylidene fluoride) and its copolymers enable the development of flexible piezoelectric devices for a wide range of applications, including wearable electronics, human-machine interfaces, energy harvesting, soft robotics, and ultrasonic imaging. This talk will describe our recent efforts on the improvements of piezoelectric coefficients and elastic energy densities of PVDF-based ferroelectric polymers and composites. Inspired by the morphotropic phase boundary (MPB), a critical concept in the design of high-performance piezoelectric ceramics, we establish the coexistence regions of the competing ferroelectric and relaxor properties in the P(VDF-TrFE) copolymers and reveal the crucial role of chain tacticity in driving the formation of the transition region. The copolymer with the morphotropic composition exhibits state-of-the-art piezoelectric coefficients. We employ an electro-thermal approach to drive the ferroelectric phase transition in PVDF-based percolative polymer nanocomposites. The actuators based on electro-thermal actuation outperform current polymer-based actuators in terms of concurrently enhanced actuation strain and elastic energy density that are triggered at a much lower electric field. In this regard, electro-thermal actuators based on ferroelectric polymer nanocomposites can bridge the gap between ferroelectric polymers and piezoelectric ceramics. This talk will discuss fundamental insights into the structural mechanisms that control piezoelectricity and actuations in ferroelectric polymers.
