期刊
Science
标题
Fluoropolymer ferroelectrics: Multifunctional platform for polar-structured energy conversion
作者
XIAOSHI QIAN, XIN CHEN, LEI ZHU, AND Q. M. ZHANG
摘要
BACKGROUND
Polymeric ferroelectrics are distinguished by their high pliability, easy fabrication into complicated shapes, mechanical robustness, and polar active nature. Ferroelectricity in polymers was discovered around the 1970s in poly(vinylidene fluoride), which has served as a platform for efficient cross-coupling between electrical, mechanical, and thermal energies. Such ferroelectric soft materials and their polar active derivatives undergo a change in electrical polarization in response to general forces (mechanical stresses or temperature changes) and vice versa, enabling a series of physical effects, including piezoelectric and electrostriction, electrocaloric and pyroelectric, and a variety of dielectric and ferroelectric effects. These multifunctional polymeric materials are suitable for many different applications in portable, miniaturized, and wearable electroactive devices applied at human–machine interfaces because of their easy processability into thin, light, tough, and pliable films and fibers.
ADVANCES
Polymer ferroelectrics have exhibited marked improvements in electromechanical coupling efficiency, electrostrictive strain, electrocaloric heat-pumping capability, and lifetime, which have substantially boosted the development of practical applications based on these polar soft materials owing to the facile application of defects in tuning and controlling the polarization processes at the monomeric, macromolecular, and morphological structure levels. For the first time, the piezoelectric and electromechanical coupling factors of fluorinated alkyne (FA)–modified relaxor ferroelectric tetrapolymers have surpassed those of lead zirconate titanate (PZT) piezoceramics, the presently most widely used piezoceramics in the world. Coupled with the progressive 4% electrostrictive strain under a low electrical field of 50 MV/m, this advancement represents a step forward in developing efficient wearable sensory and haptic devices and soft robots. Additionally, advances in ferroelectric-based electrocaloric
OUTLOOK
Understanding and then tailor-making the structures and polarization responses of polymeric ferroelectrics to obtain respective functionalities are critical for the development of these polymeric systems. Given their rich underlying chemistry, FA-modified relaxor ferroelectric polymers are likely still in their infancy. Defect modifications on the molecular scale provide a plethora of methods to manipulate the polar structures and field-induced phase transitions on demand. Considering the vast pool of monomers and nanoscale extrinsic inclusions that can be selected, defect modification in polymer ferroelectrics remains largely unexplored and holds great possibility for contributing to green, smart, and meta lifestyles. Further identifying and understanding the various polarization mechanisms and processes for each functionality at multiple scales will be accomplished by utilizing the current advanced, in situ characterization and simulation tools at our disposal. For different cross-couplings and correlated applications, materials should be fine-tuned to exhibit their respective collection of optimized properties. Several mutual challenges should be addressed, including realizing low-field operation, a long lifetime, viable strategies for integration and mass production, and so on. Considering the commercially available processes for polymeric films, multilayer capacitors, fibers, and fabrics, these flexible ferroelectrics are expected to play a key role in haptic, sensory, and robotic applications in the metaverse, serve as a solid-state refrigerant for flat-panel and/or wearable ACs, and provide a broad range of localized, bodily sensations and tactile effects currently unavailable on the market.
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