Intrinsic and Extrinsic Losses in Nanoelectromechanical Systems

纳米机电系统的内在和外在损耗

• 批准号: 1506619
• 负责人: Narayana Aluru
• 金额: $ 36.28万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1506619&HistoricalAwards=false
• 关键词: Intrinsic; Extrinsic; Losses; Nanoelectromechanical; Systems

Title: Intrinsic and Extrinsic Losses in Nanoelectromechanical SystemsProject Goals:To develop a fundamental understanding of energy losses in nanostructures and to exploit this knowledge for enhanced performance of nanostructuresNontechnical Abstract:Nanoelectromechanical systems (NEMS) have attracted significant interest as they promise high frequencies and quality factors (Q). However, many recent experimental studies have observed that the mechanical quality factor, Q, defined as the ratio of the energy stored to the energy lost per unit period, of NEMS is much lower than those from theoretical predictions. This discrepancy can be attributed to the novel physics that arises at the nanoscale and is not accounted for in the classical theory. The attainable frequencies in NEMS are comparable to the phonon frequencies and this can introduce new sources of intrinsic dissipation, such as Akhiezer damping, which can significantly reduce the quality factors. In addition, as the surface to volume ratio is higher at nanoscale, surfaces act as an additional source of dissipation reducing the Q. To realize the full potential of NEMS, it is important to develop a comprehensive physical understanding of all dissipation mechanisms at nanoscale. Through this knowledge, high Q nanostructures can be engineered. Since classical theories do not adequately describe dissipation at nanoscale, the focus of this project is to develop atomistic and multiscale approaches to understand dissipation in nanostructures.This project will provide interdisciplinary research, education and training of graduate and undergraduate students and the research results will be widely disseminated for broader impact.Technical Abstract:Two types of mechanical losses, namely intrinsic and extrinsic, will be considered and understood. Intrinsic losses or energy dissipation mechanisms are those that are inherent to the nanostructure. Popular sources of intrinsic dissipation are Akhiezer damping, thermo-elastic damping, surfaces, defects, etc. Most nanostructures operate in a fluid medium, so in addition to intrinsic losses, extrinsic losses, defined as the dissipation caused by the fluid, also needs to be taken into account. The key objectives of this project are to (i) Develop atomistic and multiscale computational approaches to understand intrinsic losses in a variety of one-dimensional and two-dimensional nanostructures. Comprehensive theories to model Akhiezer, thermo-elastic, defects, surfaces and other sources of intrinsic dissipation will be developed. (ii) Develop atomistic and multiscale computational approaches to understand extrinsic losses. To determine extrinsic losses, coupled fluidic and structural analysis is necessary. To compute fluidic forces acting on the nanostructure, a comprehensive multiscale approach will be developed. The multiscale approach for fluidic analysis will be coupled with a multiscale approach for nanostructural analysis to determine extrinsic losses. (iii) Establish validation of the computational approaches by comparing computed quality factors with experimental data. In addition, various applications of NEMS such as high frequency resonators, energy harvesting and mass sensing will be pursued.

项目目标：对纳米结构中的能量损失有一个基本的了解，并利用这些知识来增强纳米结构的性能。摘要：纳米机电系统（NEMS）因其承诺高频率和高质量因子(Q)而引起了人们的极大兴趣。然而，最近的许多实验研究发现，NEMS的机械质量因子Q（定义为单位周期内储存的能量与损失的能量之比）远低于理论预测。这种差异可以归因于在纳米尺度上出现的新物理学，而在经典理论中没有得到解释。NEMS中可达到的频率与声子频率相当，这可以引入新的固有耗散源，例如Akhiezer阻尼，这可以显着降低质量因素。此外，由于纳米尺度下的表面体积比更高，表面作为额外的耗散源降低了q。为了充分发挥NEMS的潜力，对纳米尺度下的所有耗散机制有一个全面的物理理解是很重要的。通过这些知识，高Q纳米结构可以被设计出来。由于经典理论不能充分描述纳米尺度的耗散，本项目的重点是发展原子和多尺度的方法来理解纳米结构中的耗散。该项目将为研究生和本科生提供跨学科的研究、教育和培训，研究成果将广泛传播，产生更广泛的影响。技术摘要：两种类型的机械损失，即内在和外在，将考虑和理解。固有损耗或能量耗散机制是纳米结构所固有的。常见的本征耗散源有阿希泽阻尼、热弹性阻尼、表面、缺陷等。大多数纳米结构在流体介质中工作，因此除了固有损失外，还需要考虑外在损失，即流体引起的耗散。该项目的主要目标是：(i)发展原子和多尺度计算方法，以了解各种一维和二维纳米结构的内在损失。将发展综合理论来模拟Akhiezer，热弹性，缺陷，表面和其他本征耗散源。发展原子和多尺度计算方法来理解外在损失。为了确定外在损失，必须对流体和结构进行耦合分析。为了计算作用在纳米结构上的流体力，将发展一种综合的多尺度方法。流体分析的多尺度方法将与纳米结构分析的多尺度方法相结合，以确定外在损失。（iii）通过将计算的质量因子与实验数据进行比较，建立计算方法的有效性。此外，NEMS的各种应用，如高频谐振器，能量收集和质量传感将被追求。