Nag Sarthak, Tomo Yoko, Teshima Hideaki, Takahashi Koji, Kohno Masamichi
Department of Mechanical Engineering, Kyushu University, Fukuoka 819-0395, Japan.
International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, Fukuoka 819-0395, Japan.
Phys Chem Chem Phys. 2021 Nov 10;23(43):24652-24660. doi: 10.1039/d1cp03451k.
Probing the dynamics of nanobubbles is essential to understand their longevity and behavior. Importantly, such an observation requires tools and techniques having high temporal resolutions to capture the intrinsic characteristics of the nanobubbles. In this work, we have used the liquid-phase electron microscopy (LPEM) technique to gain insights into nanobubbles' behavior and their interfacial dynamics. Interestingly, we could observe a freely growing-shrinking nanobubble and a pinned nanobubble under the same experimental conditions, suggesting the possibility of multiple nanobubble stabilization theories and pathways. Remarkably, the study reveals that a freely growing-shrinking nanobubble induces anisotropic depinning in the three-phase contact line of a strongly pinned neighboring nanobubble. The anisotropic depinning is attributed to the differential local gas saturation levels, depending on the relative positioning of the freely growing-shrinking nanobubble. Furthermore, we also observed a unique pull-push phenomenon exhibited by the nanobubble's interfaces, which is attributed to the van der Waals interactions and the electric double layer collectively. The role of the electric double layer in suppressing and delaying the merging is also highlighted in this study. The present work aims to reveal the role of locally varying gas saturation in the depinning of nanobubbles, their longevity due to the electric double layer, and the consequent coalescence, which is crucial to understand the behavior of the nanobubbles. Our findings will essentially contribute to the understanding of these novel nanoscale gaseous domains and their dynamics.
探究纳米气泡的动力学对于理解它们的寿命和行为至关重要。重要的是，这样的观察需要具有高时间分辨率的工具和技术来捕捉纳米气泡的内在特征。在这项工作中，我们使用了液相电子显微镜（LPEM）技术来深入了解纳米气泡的行为及其界面动力学。有趣的是，在相同的实验条件下，我们可以观察到一个自由生长-收缩的纳米气泡和一个固定的纳米气泡，这表明存在多种纳米气泡稳定理论和途径的可能性。值得注意的是，该研究表明，一个自由生长-收缩的纳米气泡会在一个强烈固定的相邻纳米气泡的三相接触线处诱导各向异性脱钉。这种各向异性脱钉归因于局部气体饱和度的差异，这取决于自由生长-收缩的纳米气泡的相对位置。此外，我们还观察到纳米气泡界面表现出的一种独特的推拉现象，这是由范德华相互作用和双电层共同作用引起的。本研究还强调了双电层在抑制和延迟合并中的作用。目前的工作旨在揭示局部变化的气体饱和度在纳米气泡脱钉中的作用、由于双电层导致的它们的寿命以及随之而来的合并，这对于理解纳米气泡的行为至关重要。我们的发现将从根本上有助于理解这些新型纳米级气态域及其动力学。
