Jiang Pengcheng, Chen Rong, Zhu Xun, Ye Dingding, Yang Yang, Wang Hong, Li Haonan, Yang Yijing, Liao Qiang
Key Laboratory of Low-grade Energy Utilization Technologies and Systems (Chongqing University), Ministry of Education, Chongqing 400030, China.
Institute of Engineering Thermophysics, School of Energy and Power Engineering, Chongqing University, Chongqing 400030, China.
J Phys Chem Lett. 2022 Jun 2;13(21):4762-4767. doi: 10.1021/acs.jpclett.2c01079. Epub 2022 May 25.
Light droplet levitation is an elegant technique allowing for contact-less manipulation in a wall-free environment. However, direct generation of light levitated droplets remains limited by small-curvature interface and underlying mechanism remains unclear. Here we report that small-curvature interface limitation encountered in liquid water is overcome by using liquids with extremely small saturated vapor pressure, which allows for direct generation of light levitated droplets above large-curvature interface. It is demonstrated that the interface morphology and extremely small saturated vapor pressure of liquids together contribute to creation of the gravity-lift and evaporation-condensation balances, enabling droplet levitation even above large-curvature interface. We also propose a levitation number to judge whether droplets can be directly levitated above a curved interface or not, which successfully predicts the occurrence of light droplet levitation. When falls in the range of 2.25 × 10 ∼ 6 × 10, tiny condensed droplets can be stably levitated above the gas-liquid interface no matter interface morphology and liquid type. The study deepens the understanding of the underlying mechanism for generating light levitated droplets.
轻液滴悬浮是一种精巧的技术，可在无壁环境中进行非接触式操控。然而，轻悬浮液滴的直接产生仍受小曲率界面的限制，其潜在机制尚不清楚。在此我们报告，通过使用具有极小饱和蒸气压的液体，克服了液态水中遇到的小曲率界面限制，这使得在大曲率界面上方能够直接产生轻悬浮液滴。结果表明，液体的界面形态和极小饱和蒸气压共同促成了重力提升与蒸发 - 冷凝平衡的建立，即使在大曲率界面上方也能实现液滴悬浮。我们还提出了一个悬浮数来判断液滴是否能在弯曲界面上方直接悬浮，该悬浮数成功预测了轻液滴悬浮的发生。当悬浮数落在2.25×10～6×10范围内时，无论界面形态和液体类型如何，微小的冷凝液滴都能稳定地悬浮在气 - 液界面上方。该研究加深了对产生轻悬浮液滴潜在机制的理解。
