In situ scanning electron microscopy observations of filler material transport in branched carbon microtubes by Joule heating.
In situ scanning electron microscopy observations of filler material transport in branched carbon microtubes by Joule heating.
复制标题
DOI：
10.1093/jmicro/dfaa023
复制
发表时间：
2020-05
期刊：
影响因子：
1.8
通讯作者：
M. Okada;Daiya Sasaki;H. Kohno
中科院分区：
文献类型：
--
作者：
M. Okada;Daiya Sasaki;H. Kohno
制备了具有金属填充材料的Y支化或并排支化碳微管，并用带微电极探针的原位扫描电子显微镜研究了焦耳加热条件下支化碳微管中的物质输运。当施加电压和电流时，包裹在微管中的材料会从原来的位置移动。这一运动与电流的方向无关；因此，得出结论，这种运动不是由于电迁移，而是由于焦耳加热导致的温度梯度、体积膨胀和蒸汽压升高。在Y形分支微管中，金属填充材料的一部分从一个分支移动到另一个分支，这将有助于微流控流量切换。还观察到圆柱形的填充材料在保持形状的同时从树枝上排出，这种现象可能是由汽化诱导的高压引起的，并可应用于微机械操作器，如打孔针。在并排分支的碳微管中，焦耳加热导致热体积膨胀，以填充最初空置的分支中的空间。然后，当电流关闭时，微管恢复到与初始状态几乎相同的空隙状态。这些结果表明，热体积膨胀可用于流动切换。
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.