Institute of Low Temperature Science, Hokkaido University, Sapporo, Hokkaido, Japan.
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, Japan.
Microscopy (Oxf). 2022 Aug 1;71(4):231-237. doi: 10.1093/jmicro/dfac021.
Liquid-cell transmission electron microscopy (LC-TEM) is a useful technique for observing phenomena in liquid samples with spatial and temporal resolutions similar to those of conventional transmission electron microscopy (TEM). This method is therefore expected to permit the visualization of phenomena previously inaccessible to conventional optical microscopy. However, dynamic processes such as nucleation are difficult to observe by this method because of difficulties in controlling the condition of the sample liquid in the observation area. To approach this problem, we focused on dielectrophoresis, in which electrodes are used to assemble particles, and we investigated the phenomena that occurred when an alternating-current signal was applied to an electrode in an existing liquid cell by using a phase-contrast optical microscope (PCM) and TEM. In PCM, we observed that colloidal particles in a solution were attracted to the electrodes to form assemblies, that the particles aligned along the electric field to form pearl chains and that the pearl chains accumulated to form colloidal crystals. However, these phenomena were not observed in the TEM study because of differences in the design of the relevant holders. The results of our study imply that the particle assembly by using dielectrophoretic forces in LC-TEM should be possible, but further studies, including electric device development, will be required to realize this in practice.
液相透射电子显微镜（LC-TEM）是一种有用的技术，可用于观察具有类似于传统透射电子显微镜（TEM）的空间和时间分辨率的液相样品中的现象。因此，预计该方法可使以前无法用传统光学显微镜观察到的现象可视化。然而，由于难以控制观察区域中样品液体的条件，因此难以通过该方法观察诸如成核等动态过程。为了解决此问题，我们专注于电动力学，其中使用电极来组装颗粒，并且我们通过使用相差光学显微镜（PCM）和 TEM 研究了当在现有液相池中向电极施加交流信号时发生的现象。在 PCM 中，我们观察到溶液中的胶体颗粒被吸引到电极上以形成组装体，颗粒沿电场排列形成珍珠链，并且珍珠链积累形成胶体晶体。然而，由于相关支架的设计差异，在 TEM 研究中未观察到这些现象。我们的研究结果表明，使用 LC-TEM 中的电动力学力进行颗粒组装应该是可能的，但是需要进一步的研究，包括电设备的开发，才能在实践中实现这一目标。
