Recent Advances in Ferroelectret Fabrication, Performance Optimization, and Applications
Ningzhen Wang (Beijing Forestry University)
He Zhang (Beijing Forestry University)
Xunlin Qiu (East China University of Science and Technology)
Reimund Gerhard (University of Potsdam)
Jan Van Turnhout (TU Delft - Team Erik Offerman)
Jason Cressotti (University of Connecticut)
Dong Zhao (Beijing Forestry University)
Liang Tang (Beijing Forestry University)
Yang Cao (University of Connecticut)
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Abstract
The growing demand for wearable devices has sparked a significant interest in ferroelectret films. They possess flexibility and exceptional piezoelectric properties due to strong macroscopic dipoles formed by charges trapped at the interface of their internal cavities. This review of ferroelectrets focuses on the latest progress in fabrication techniques for high temperature resistant ferroelectrets with regular and engineered cavities, strategies for optimizing their piezoelectric performance, and novel applications. The charging mechanisms of bipolar and unipolar ferroelectrets with closed and open-cavity structures are explained first. Next, the preparation and piezoelectric behavior of ferroelectret films with closed, open, and regular cavity structures using various materials are discussed. Three widely used models for predicting the piezoelectric coefficients (d33) are outlined. Methods for enhancing the piezoelectric performance such as optimized cavity design, utilization of fabric electrodes, injection of additional ions, application of DC bias voltage, and synergy of foam structure and ferroelectric effect are illustrated. A variety of applications of ferroelectret films in acoustic devices, wearable monitors, pressure sensors, and energy harvesters are presented. Finally, the future development trends of ferroelectrets toward fabrication and performance optimization are summarized along with its potential for integration with intelligent systems and large-scale preparation.