Collaborative Research: Generating Electricity from Deformation: Multiscale Modeling and Characterization of Flexoelectricity from Atoms to Devices

微型或纳米级的小型传感器有望将人类感知扩展到极端和以前无法进入的环境。这些下一代独立传感器系统将如何供电？许多现有的解决方案使用压电材料将机械振动转换成电力。然而，只有一小类材料表现出这种形式的机电耦合的实际有用水平，并且这些材料通常在较高温度下失去压电性。这就排除了它们在最需要新型传感器的环境中的使用。此外，性能最高的压电材料含有铅，这会造成制造和处置危险。该项目研究了通过一种完全不同的现象发电，称为挠曲发电。与压电不同，挠曲电存在于所有介电固体中，因此提供了压电的环境兼容替代品。该项目结合了互补的计算和实验研究，以探索和理解从原子尺度到设备水平的挠曲电。这项工作将使一个新的框架，大大提高性能的能量收集设备。该合作研究计划结合了原子和连续电弹性建模，非线性动力学现象，纳米纤维，多尺度实验和设备表征，以促进建立一类新型的革命性自供电传感器和小规模传感系统。通过将原子论和连续统理论与严格的实验相结合，将建立一个完全耦合的挠曲电能量采集器框架，以探索转换效率和功率密度的比例律。对于高的激励水平，非线性弹性，电弹性，和耗散效应在flexoelectric能量收集的特点。基于这种从根本上变革的机电能量收集方法，柔性电和基于连续的能量收集模型的原子模型将与实验协同耦合，以建立下一代能量收集器。线性和非线性宽带架构将探索收获确定性和随机振动能量。这项研究还将建立一个框架，并在各种其他问题中使用的纳米结构的电弹性动力学的透彻理解，涉及双向机电耦合（如传感，驱动，控制）在亚微米尺度。

Small sensors -- at the micro or nanoscale -- promise to extend human perception to extreme and previously inaccessible environments. How will these next-generation stand-alone sensor systems be powered? Many existing solutions use piezoelectric materials to convert mechanical vibration into electricity. However, only a small class of materials exhibits practically useful levels of this form of electromechanical coupling, and those typically lose their piezoelectricity at higher temperatures. This precludes their use in precisely the environments where the new classes of sensors are needed most. Furthermore, the highest performing piezoelectric materials contain lead, which creates manufacturing and disposal hazards. This project investigates generation of electricity by an entirely different phenomenon, called flexoelectricity. Unlike piezoelectricity, flexoelectricity is present in all dielectric solids, and thus offers an environmentally compatible alternative to piezoelectrics. This project combines complementary computational and experimental research studies to explore and understand flexoelectricity from atomistic scales to the device level. This work will enable a novel framework for the dramatically enhanced performance of energy harvesting devices. This collaborative research program combines atomistic and continuum electroelastic modeling, nonlinear dynamic phenomena, nanofabrication, multi-scale experiments, and device characterization to facilitate the establishment of a novel class of revolutionary self-powered sensors and sensing systems at small scales. By bridging the atomistic and continuum theories with rigorous experiments, a fully coupled flexoelectric energy harvester framework will be established to explore the scaling laws for conversion efficiency and power density. For high excitation levels, nonlinear elastic, electroelastic, and dissipative effects in flexoelectric energy harvesting will also be characterized. Based on this fundamentally transformative approach to electromechanical energy harvesting, atomistic modeling of flexoelectricity and continuum-based energy harvesting models will be synergistically coupled with experiments to establish next-generation energy harvesters. Both linear and nonlinear broadband architectures will be explored for harvesting deterministic and stochastic vibrational energy. This research will also establish a framework and thorough understanding of the electroelastic dynamics of nanostructures for use in a variety of other problems involving two-way electromechanical coupling (e.g. sensing, actuation, control) at submicron scales.