We describe a novel rotating trait of induced-charge electroosmotic slip above a planar metal surface, a phenomenon termed “Rotating induced-charge electro-osmosis” (ROT-ICEO), in the context of a new microfluidic technology for tunable particle rotation or rotational trap. ROT-ICEO has a dynamic flow stagnation line (FSL) that rotates synchronously with a background circularly polarized electric field. We reveal that the rotating FSL of ROT-ICEO gives rise to a net hydrodynamic torque that is responsible for rotating fluids or particles in the direction of the applied rotating electric field either synchronously or asynchronously, the magnitude of which is adjusted by a balance between rotation of FSL and amplitude of angular-direction flow component oscillating at twice the field frequency. Supported by experimental observation, our physical demonstration with ROT-ICEO proves invaluable for the design of flexible electrokinetic framework in modern microfluidic system.

Nanoparticle (NP), as a kind of hard-to-machine component in nanofabrication processes, dramatically affects the machined surface quality in nano-cutting. However, the surface/subsurface generation and the plastic deformation mechanisms of the workpiece still remain elusive. Here, the nano-cutting of a single-crystalline copper workpiece with a single spherical embedded nanoparticle is explored using molecular dynamics (MD) simulations. Four kinds of surface/subsurface cases of nanoparticle configuration are revealed, including being removed from the workpiece surface, moving as a part of the cutting tool, being pressed into the workpiece surface, and not interacting with the cutting tool, corresponding to four kinds of relative depth ranges between the center of the nanoparticle and the cutting tool. Significantly different plastic deformation mechanisms and machined surface qualities of the machined workpiece are also observed, suggesting that the machined surface quality could be improved by adjusting the cutting depth, which results in a change of the relative depth. In addition, the nanoparticle also significantly affects the processing forces in nano-cutting, especially when the cutting tool strongly interacts with the nanoparticle edge.

化学气相沉积法是大面积、高质量石墨烯沉积制备实践中的重要方法. 本文采用分子动力学仿真技术, 模拟了利用化学气相沉积法在铜(111)晶面制备石墨烯的过程, 研究揭示了石墨烯在铜(111)晶面上的微观生长机理. 研究结果表明: 石墨烯的沉积生长可描述为第一阶段的二元碳、三元碳和碳链形成阶段, 以及第二阶段的碳环生成以及缺陷愈合阶段. 研究发现沉积过程中的高温能够给碳原子提供足够的能量, 使其越过两个阶段之间的能量障碍, 实现石墨烯的沉积生长. 探究了温度与碳沉积速率对石墨烯的影响, 发现温度的影响主要体现在石墨烯的缺陷以及表面平整度两个方面. 在1300 K的温度下生长的石墨烯缺陷较少, 平整度最好. 碳沉积速率会影响石墨烯生长过程中出现的缺陷, 仿真获得了石墨烯最佳表面平整度时的碳沉积速率为5 ps^–1. 本文的研究结果对铜基底表面化学气相沉积法制备石墨烯的实际应用具有指导意义.

Polycrystalline materials like Cu–Pb alloy consist of four types of microstructural components, including grain cells, grain boundaries, triple junctions and vertex points, the mechanical properties of which governed by the atomic proportion of the alloy elements to a certain degree. The internal stresses from such microstructural components are quite different. Due to experimental limitations, the internal stresses from the alloy materials are difficult to measure directly, especially in the microstructural components. Here, we report a bottom-up approach using an atomistic calculation to obtain atomic properties in Cu-based alloy, as well as that in the microstructural components. The results reveal that a steep stress gradient exists at the interfaces of the alloy, which decreases significantly with the increase of the Pb. The defects evolution process in the alloy samples are investigated during tensile loading, revealing that the defect nucleation is delayed due to the decreasing von Mises stress gradient in the interfaces region as Pb increased. And the increased hydrostatic pressure in the interfaces regions, as a secondary factor can promote the defect nucleation. Among alloy samples with a grain size of 18.58 nm, that with 6.6 at.% Pb has minimal defects and the best mechanical properties.