Chiu Yu-Tung, Hsiao Ya-Lin, Morita Yuki, Ohmura Naoto, Sun Chen-Li
Department of Mechanical Engineering, National Taiwan University, Taipei, 106319, Taiwan.
Department of Chemical Science and Engineering, Kobe University, Kobe, 657-8501, Japan.
Sci Rep. 2025 May 23;15(1):18038. doi: 10.1038/s41598-025-02940-w.
Leidenfrost drop can accelerate chemical reactions, offering great potential for droplet-based chemical reactors. By leveraging their motion on heated surfaces with micro-rachets, we demonstrate that mixing can be further enhanced through head-on collisions of two Leidenfrost drops. This study identifies three mixing stages. In Stage I, collision dynamics and film drainage between drops control coalescence, with surface tension disparities prolonging Stage I for heterogeneous drops. Stage II is driven by advective transport, though viscous effect from deformation can slow internal flow. In Stage III, oscillations promote mixing. For identical drops, complete mixing can be achieved within 2-3 oscillations. However, when drops with different boiling points collide, bubble nucleation emerges from the contact surface. Boiling not only prolongs the transition to Stage III or even disrupts stable oscillations but also hinders mixing through selective evaporation. In this study, the most rapid mixing occurs when two 10 µl Leidenfrost drops of water coalesce. Complete mixing is achieved within 100 ms, about two orders of magnitude faster than conventional methods. The results provide insights into optimizing Leidenfrost drop reactors and highlight the benefits of the extreme mobility of the Leidenfrost state for applications requiring rapid mixing.
莱顿弗罗斯特液滴可以加速化学反应，为基于液滴的化学反应器提供了巨大潜力。通过利用微棘轮在加热表面上的运动，我们证明了两个莱顿弗罗斯特液滴的正面碰撞可以进一步增强混合效果。本研究确定了三个混合阶段。在第一阶段，液滴之间的碰撞动力学和液膜排水控制着聚结过程，表面张力差异会延长异质液滴的第一阶段。第二阶段由平流输运驱动，尽管变形产生的粘性效应会减缓内部流动。在第三阶段，振荡促进混合。对于相同的液滴，在2 - 3次振荡内可以实现完全混合。然而，当沸点不同的液滴碰撞时，接触表面会出现气泡成核现象。沸腾不仅会延长向第三阶段的过渡时间，甚至会破坏稳定的振荡，还会通过选择性蒸发阻碍混合。在本研究中，当两个10微升的莱顿弗罗斯特水滴聚结时，混合速度最快。在100毫秒内实现完全混合，比传统方法快约两个数量级。这些结果为优化莱顿弗罗斯特液滴反应器提供了见解，并突出了莱顿弗罗斯特状态的极高流动性在需要快速混合的应用中的优势。
