Zhao Lei, Seshadri Serena, Liang Xichen, Bailey Sophia J, Haggmark Michael, Gordon Michael, Helgeson Matthew E, Read de Alaniz Javier, Luzzatto-Fegiz Paolo, Zhu Yangying
Department of Mechanical Engineering, University of California, Santa Barbara, Santa Barbara, California 93106-5070, United States.
Department of Chemistry, University of California at Santa Barbara, Santa Barbara, California 93106-5070, United States.
ACS Cent Sci. 2022 Feb 23;8(2):235-245. doi: 10.1021/acscentsci.1c01127. Epub 2022 Jan 13.
The development of noninvasive and robust strategies for manipulation of droplets and bubbles is crucial in applications such as boiling and condensation, electrocatalysis, and microfluidics. In this work, we realize the swift departure of droplets and bubbles from solid substrates by introducing photoresponsive surfactants and applying asymmetric illumination, thereby inducing a "photo-Marangoni" lift force. Experiments show that a pinned toluene droplet can depart the substrate in only 0.38 s upon illumination, and the volume of an air bubble at departure is reduced by 20%, indicating significantly faster departure. These benefits can be achieved with moderate light intensities and dilute surfactant concentrations, without specially fabricated substrates, which greatly facilitates practical applications. Simulations suggest that the net departure force includes contributions from viscous stresses directly caused by the Marangoni flow, as well as from pressure buildup due to flow stagnation at the contact line. The manipulation scheme proposed here shows potential for applications requiring droplet and bubble removal from working surfaces.
开发用于操控液滴和气泡的无创且稳健的策略，在诸如沸腾与冷凝、电催化以及微流体等应用中至关重要。在这项工作中，我们通过引入光响应表面活性剂并施加不对称光照，实现了液滴和气泡从固体基底的快速脱离，从而诱导出一种“光马兰戈尼”升力。实验表明，一个固定的甲苯液滴在光照后仅需0.38秒即可离开基底，并且气泡离开时的体积减小了20%，这表明其脱离速度显著加快。这些优点可以在适度的光强度和稀释的表面活性剂浓度下实现，无需特殊制造的基底，这极大地促进了实际应用。模拟结果表明，净脱离力包括马兰戈尼流直接引起的粘性应力贡献，以及由于接触线处流动停滞导致压力积累的贡献。这里提出的操控方案在需要从工作表面去除液滴和气泡的应用中显示出潜力。
