Low-Temperature CO2-Assisted Assembly of Cyclic Olefin Copolymer Ferroelectrets of High Piezoelectricity and Thermal Stability

A novel supercritical carbon dioxide (CO2)-assisted low-temperature assembly approach to fabricate cyclic olefin copolymer (COC) ferroelectrets is reported. The process takes advantage of the strong COC-CO2 interaction and associated severe depression of both bulk and surface glass transition temperature. Using a multilayer structural design to implement a bending mechanism in the ferroelectrets, the apparent compression modulus can be greatly reduced and tailored, leading to COC ferroelectrets with excellent piezoelectric activity. The COC ferroelectrets exhibit excellent thermal stability. The study presents a viable low-cost technology to mass produce COC ferroelectrets with high piezoelectric activity that can be used in structurally and thermally demanding conditions.