Otic Clint John Cortes, Yonemura Shigeru
Department of Finemechanics, Graduate School of Engineering, Tohoku University, 6-6 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579, Japan.
Department of Mechanical Engineering, College of Engineering, Chubu University, 1200 Matsumoto-cho, Kasugai 487-8501, Japan.
Micromachines (Basel). 2022 Jul 10;13(7):1092. doi: 10.3390/mi13071092.
In this paper, we propose that thermally induced Knudsen forces in a rarefied gas can be exploited to achieve a tweezer-like mechanism that can be used to trap and grasp a micro-object without physical contact. Using the direct simulation Monte Carlo (DSMC) method, we showed that the proposed mechanism is achieved when a heated thin plate, mounted perpendicularly on a flat substrate, is placed close to a colder object; in this case, a beam. This mechanism is mainly due to the pressure differences induced by the thermal edge flows at the corners of the beam and the thermal edge flow at the tip of the thin plate. Specifically, the pressure on the top surface of the beam is smaller than that on its bottom surface when the thin plate is above the beam, while the pressure on the right side of the beam is smaller than that on its left side when the thin plate is located near the right side of the beam. These differences in pressure generate a force, which attracts the beam to the plate horizontally and vertically. Furthermore, this phenomenon is enhanced when the height of the beam is shorter, such that the horizontal and vertical net forces, which attract the beam to the plate, become stronger. The mechanism proposed here was also found to depend significantly on the height of the beam, the temperature difference between the thin plate and the beam, and the Knudsen number.
在本文中，我们提出可以利用稀薄气体中热诱导的克努森力来实现一种类似镊子的机制，该机制可用于在不进行物理接触的情况下捕获和抓取微小物体。通过直接模拟蒙特卡洛（DSMC）方法，我们表明，当一块垂直安装在平坦基板上的加热薄板靠近一个较冷的物体（在这种情况下是一根梁）放置时，所提出的机制即可实现。这种机制主要是由于梁的角部热边缘流和薄板尖端的热边缘流所引起的压力差。具体而言，当薄板位于梁上方时，梁顶表面的压力小于其底表面的压力；而当薄板位于梁右侧附近时，梁右侧的压力小于其左侧的压力。这些压力差产生一个力，该力将梁水平和垂直地吸引向薄板。此外，当梁的高度较短时，这种现象会增强，使得将梁吸引向薄板的水平和垂直合力变得更强。这里提出的机制还被发现显著依赖于梁的高度、薄板与梁之间的温差以及克努森数。
