Okada Masaki, Sasaki Daiya, Kohno Hideo
Department of Engineering, Graduate School of Engineering, Kochi University of Technology, Kami, Kochi 782-8502, Japan.
School of Environmental Science and Engineering, Kochi University of Technology, Kami, Kochi 782-8502, Japan.
Microscopy (Oxf). 2020 Oct 30;69(5):291-297. doi: 10.1093/jmicro/dfaa023.
Y-branched or side-by-side-branched carbon microtubes with metal filler material were fabricated, and material transport in the branched microtubes with Joule heating was investigated using in situ scanning electron microscopy with micro-electrode probes. When a voltage and electric current were applied, the material enclosed in the microtubes moved from its original position. The movement was not related to the direction of the electric current; therefore, it is concluded that the movement was not due to electromigration, but rather a temperature gradient, volume expansion and increased vapor pressure by Joule heating. In Y-branched microtubes, a part of the metal filler material moved from one branch to another branch, which would be useful for microfluidic flow switching. A cylindrical filler material was also observed to be expelled from a branch while its shape was maintained, and this phenomenon is presumably caused by vaporization-induced high pressure and could find application in micro-mechanical manipulators such as punching needles. In side-by-side-branched carbon microtubes, Joule heating caused thermal volume expansion to fill the spaces in the branches that were initially empty. The microtubes then reverted to a state almost identical to the initial state with empty spaces when the electric current was turned off. These results suggest that thermal volume expansion could be employed for flow switching.
制备了带有金属填充材料的Y型分支或并排分支的碳微管，并使用带有微电极探针的原位扫描电子显微镜研究了在焦耳加热作用下分支微管中的物质传输。当施加电压和电流时，微管内封闭的物质从其原始位置移动。该移动与电流方向无关；因此，可以得出结论，该移动不是由于电迁移，而是由于温度梯度、体积膨胀以及焦耳加热导致的蒸气压增加。在Y型分支微管中，一部分金属填充材料从一个分支移动到另一个分支，这对于微流体流动切换可能是有用的。还观察到圆柱形填充材料在保持其形状的同时从一个分支中被排出，这种现象可能是由汽化引起的高压导致的，并且可以应用于诸如冲孔针之类的微机械操纵器中。在并排分支的碳微管中，焦耳加热引起热体积膨胀，以填充最初为空的分支中的空间。当电流关闭时，微管随后恢复到几乎与初始空空间状态相同的状态。这些结果表明，热体积膨胀可用于流动切换。
