CAREER: Quantifying and Exploiting Knudsen Thermal Forces in Nano/Microsystems

1055453 Alexeenko在微尺度下，即使是中等的温差也会导致气体分子和浸入气体中的固体之间的非平衡能量交换产生显著的努森力。利用努森力提供了新的机制，驱动，传感和能量收集在纳米/微系统。气体Knudsen力在气体分子平均自由程尺度上很大的热梯度存在下是很重要的，这种情况在涉及微米和亚微米尺寸结构和气体环境的各种应用中都会发生并产生。该计划中的计算和实验工作将为分析和控制当前系统中的热努森力提供一条途径，例如原子力显微镜和MEMS结构，以及未来的高精度热传感器和致动器。预测热努森力需要气相中输运过程的动力学理论描述，这超出了传统宏观计算模型的能力。计算研究的基础是确定性的解决方案的Boltzmann动力学方程耦合气固热相互作用在亚连续制度。克努森力的封闭形式模型将根据高保真度模拟开发的各种条件。该模型将通过实验测量进行验证，使用扫描激光多普勒振动测量的微结构与集成的纳米级加热器在受控的环境气体压力和热条件下，在真空探针站。实验将提供直接校准测量努森力的几何相关的实际工程纳米/微系统的应用。研究成果将被纳入分子气体动力学和纳米/微系统工程课程。将通过nanoHUB（http：//www.example.com）创建一个用于模拟N/MEMS中克努森力效应的交互式在线工具，并提供给全世界的研究和教育界。nanohub.org这项研究还与教育活动相结合，旨在吸引和留住少数民族学生，并为本科生在职业生涯的早期提供研究机会。

1055453Alexeenko At the microscale, even moderate temperature differences can result in significant Knudsen forces generated by the non-equilibrium energy exchange between gas molecules and solids immersed in the gas. Exploiting the Knudsen force offers novel mechanisms for actuation, sensing, and energy harvesting in nano/microsystems. The gas Knudsen forces are significant in the presence of thermal gradients that are large on the scale of the gas molecular mean free path. Such conditions occur and can be created in a wide variety of applications involving micron-and submicron-sized structures and a gas ambient. The aligned computational and experimental efforts in this program will provide a pathway for analysis and control of thermal Knudsen forces in current systems "such as atomic force microscopy and MEMS structures" and for future high-precision thermal sensors and actuators.Prediction of thermal Knudsen forces requires kinetic theory description of transport processes in the gas phase, which is beyond the capabilities of conventional macroscopic computational models. The basis for computational investigation is the deterministic solution of Boltzmann kinetic equations for coupled gas-solid thermal interaction in the subcontinuum regime. Closed-form models for Knudsen force will be developed based on the high-fidelity simulations for a wide range of conditions. The modeling will be validated by experimental measurements using Scanning Laser Doppler Vibrometry of microstructures with integrated nanoscale heaters under controlled ambient gas pressure and thermal conditions in a vacuum probe station. The experiments will provide direct calibrated measurements of Knudsen forces in geometries relevant for applications in practical engineered nano/microsystems. The research results will be integrated into the courses on molecular gas dynamics and nano/microsystems engineering. An interactive online tool for simulation of Knudsen force effects in N/MEMS will be created and made available to a worldwide research and education community through nanoHUB (http://nanohub.org). This research is also combined with educational activities aimed at attracting and retaining minority students and providing research opportunities for undergraduate students early in their careers.