CAREER: Geometric Control of Flexoelectricity in Patterned Dielectric Thin Films

职业：图案化介电薄膜中弯曲电的几何控制

• 批准号: 1255379
• 负责人: Nazanin Bassiri-Gharb
• 金额: $ 55万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-07-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1255379&HistoricalAwards=false
• 关键词: CAREER; Geometric; Control; Flexoelectricity; Patterned

NON-TECHNICAL DESCRIPTION: Coupling between electrical and mechanical impulses underlies the basic behavior of many sensors and actuators. Classical piezoelectric materials are based on a linear correlation between the developed charges and applied stress (sensor applications) or strain developed under an applied electric field (actuator applications). With the drive towards miniaturization for micro- and nano-electromechanical systems (MEMS and NEMS), piezoelectric materials have received additional interest because piezoelectric actuation and sensing at the nanoscale can be conducted with much higher actuation power densities than with electrostatic and magnetoelectric approaches. This finding is in contrast to classical piezoelectric materials that offer only a limited strain range, and actuating device structures offer only limited scalability below the micron level. This work aims to take advantage of novel physical phenomena, i.e. flexoelectricity (coupling between strain gradients and developed charge), emergent on the nanoscale, to develop novel electromechanical materials systems scalable to nanometer sizes, while allowing for large strains. The electromechanical response scales inversely with the dimensions of flexoelectric composites (and therefore miniaturized samples), a trend opposite to what is observed in currently-available bulk single-crystal or ceramic piezoelectrics. The response of flexoelectric composites cannot be thermally or electrically degraded, and Pb-free compositions should offer much larger electromechanical response than current Pb-based piezoelectric materials. Therefore, flexoelectric nano-composites may enable a wider range of miniaturized applications and an environmentally-safe alternative to current bulk sensors and actuators.TECHNICAL DETAILS: This research aims to achieve fundamental understanding of flexoelectricity as a contributor to the electromechanical response of all dielectrics, and to harness it as a new transduction approach for micro- and nano-systems. The combination of precise nano-manufacturing methods with rigorous dielectric and (micro- and macro-scale) piezoelectric characterization, in addition to exhaustive microstructural characterization will provide a major insight into the multiscale science of flexoelectric composites. This research aims to establish theoretical and experimental limits for high electromechanical response through flexoelectricity in micro- and nano-meter patterned dielectrics, and correlate dielectric (microstructural) and flexoelectric (geometric) scaling effects to understand their co-regulation of the effective piezoelectric response in flexoelectric patterned dielectrics. A new understanding of flexoelectricity facilitates the required departure from lead-containing crystals, which remain the cornerstone of ceramic sensors and actuators. Flexoelectric coupling provides a potentially transformative companion to the conventional approaches of solid-solution engineering once the relationships between strain gradients, nanostructure, and phase transitions are well understood. An integral part of this project is the recruitment and retention of women in science and engineering. This objective is achieved through hands-on workshops (focused on smart materials) targeted to groups of girls in grades 5-12, as well as mentorship, research and education activities targeted at graduate and undergraduate students in cutting-edge scientific and technological fields.

非技术描述：电气和机械脉冲之间的耦合是许多传感器和执行器的基本行为的基础。经典压电材料基于产生的电荷与施加的应力（传感器应用）或在施加的电场下产生的应变（执行器应用）之间的线性相关性。 随着微纳机电系统（MEMS 和 NEMS）小型化的发展，压电材料受到了更多的关注，因为纳米级的压电驱动和传感可以比静电和磁电方法更高的驱动功率密度进行。这一发现与仅提供有限应变范围的经典压电材料形成对比，并且驱动装置结构仅提供微米级以下的有限可扩展性。这项工作的目的是利用纳米尺度上出现的新物理现象，即挠曲电（应变梯度和产生的电荷之间的耦合），开发可扩展到纳米尺寸的新型机电材料系统，同时允许大应变。机电响应与挠曲电复合材料（以及因此小型化的样品）的尺寸成反比，这一趋势与目前可用的块状单晶或陶瓷压电体中观察到的趋势相反。挠曲电复合材料的响应不会因热或电而降低，并且无铅组合物应提供比当前基于铅的压电材料大得多的机电响应。因此，柔性电纳米复合材料可以实现更广泛的小型化应用，并成为当前散装传感器和执行器的环保替代品。技术细节：本研究旨在对柔性电作为所有电介质机电响应的贡献者有一个基本的了解，并将其作为微纳米系统的一种新的转换方法。除了详尽的微观结构表征之外，精密纳米制造方法与严格的介电和（微观和宏观）压电表征的结合将为挠曲电复合材料的多尺度科学提供重要的见解。本研究旨在通过微米和纳米图案化电介质中的挠曲电建立高机电响应的理论和实验极限，并将电介质（微观结构）和挠曲电（几何）缩放效应关联起来，以了解它们对挠曲电图案化电介质中有效压电响应的共同调节。对挠曲电的新理解有助于摆脱含铅晶体，而含铅晶体仍然是陶瓷传感器和执行器的基石。一旦充分理解了应变梯度、纳米结构和相变之间的关系，挠曲电耦合将为传统的固溶体工程方法提供潜在的变革性伴侣。 该项目的一个组成部分是招聘和保留科学和工程领域的女性。这一目标是通过针对 5-12 年级女生群体的实践研讨会（重点是智能材料）以及针对尖端科技领域的研究生和本科生的指导、研究和教育活动来实现的。