A First-Principles Study of Electro-Mechanical Coupling in Triboelectric Nanogenerators

摩擦电效应是一种现象，一种材料通过摩擦接触到另一种材料后带电的现象，自古希腊时代以来就已为人所知。不同表面之间的机械接触是生活中无处不在的一部分，因此电荷不断积累。收集这种积累的电荷为以非常小的规模运行的设备提供了发电的机会。由于纳米技术的出现，理解和利用这一现象的工具直到最近十年才变得可用。这项基础性研究将提供一个基于互补建模和实验的理论框架，这将使研究团队能够设计出能够以更可控的方式获取大量电力的“摩擦电动纳米发电机”。摩擦电纳米发电机已经显示出高达1.2kW/m2的面向功率密度，高达490kW/m~3的体积功率密度(与氢的恒星聚变~276.5 W/m~3相比)，以及类似的非常高的能量转换效率~50-85%。从不同的表面收集这种固有的能量是这项研究的核心，可能会给经济和社会带来红利。这项研究将涉及多个学科，包括接触力学、固体力学、材料科学、电气工程和制造。这个项目还将通过直接参与和曝光来促进和扩大未被充分代表的群体对研究和教学的参与。本项目的目标是通过第一原理研究的透镜，从理论和实验两个方面了解摩擦带电的基本机制和摩擦电纳米发电机中的表面电荷密度。研究小组将结合精心设计的实验进行第一性原理模拟，以：(1)推导出原子论的电动力学理论并将其整合到可直接与实验进行比较的模拟中，从而建立理论和实验之间的基线；(2)研究接触模式摩擦带电的充电机制，并将法向应变与诱导的束缚电荷相关联；(3)将滑动模式摩擦带电与剪切应变、表面粗糙度、摩擦循环和收获效率联系起来。

The triboelectric effect, a phenomenon wherein one material becomes electrically charged after it contacts a different material through friction, has been known since the times of ancient Greece. Mechanical contact between dissimilar surfaces is a ubiquitous part of life and thus a buildup of electric charge is constantly happening. Harvesting of this buildup of electrical charge provides an opportunity for the generation of electricity for devices that operate at very small scales. The tools for understanding and capitalizing on this phenomenon have only become available in the last decade due to the advent of nanotechnology. This fundamental research will provide a theoretical framework based on complementary modeling and experiments, which will allow the research team to engineer "triboelectric nanogenerators" that are capable of harvesting significant amounts of power in a more controlled way. Triboelectric nanogenerators have demonstrated a high area-wise power density of up to 1.2 kW/m2, a volume-wise power density of up to 490 kW/m3 (compare this to the stellar fusion of hydrogen ~276.5 W/m3), and similarly a very high energy conversion efficiency of ~50-85%. Harvesting of this energy that is inherently available from dissimilar surfaces is central to this research and can potentially pay dividends to the economy and society. This research will involve many disciplines including contact mechanics, solid mechanics, materials science, electrical engineering, and manufacturing. Participation of underrepresented groups in research and pedagogy will also be facilitated and broadened in this program through direct participation and exposure.The goal of this project is to understand the fundamental mechanism of triboelectrification and the surface charge density in triboelectric nanogenerators through the lens of a first-principles investigation, both theoretically and experimentally. The research team will perform first-principles simulations in conjunction with carefully designed experiments to: (1) derive an atomistic electrodynamic theory and integrate it into simulations that are directly compared to experiments thereby establishing a baseline between theory and experiment; (2) investigate the charging mechanism of contact mode triboelectrification and correlate normal strain with the induced, bound charges; and (3) relate the charging mechanism of sliding mode triboelectrification with shear strain, surface roughness, friction cycles and harvesting efficiency.