Abstract:

High-speed cameras were used to capture the impact of deionized water droplets, three relative molecular masses of polyethylene oxide (PEO) droplets, bis(2-ethylhexyl)sulfosuccinate (AOT) droplets of surfactant and a combination of two additives on the surface of lotus leaves. Comparative analysis of the deposition characteristics of droplets with different characteristics on the leaf surface were studied by comparative analysis. The experimental results showed that PEO additives could significantly inhibit droplet rebound and increase droplet residence time on leaf surface, and prevent outward emission of satellite droplets. The inhibition effect of high relative molecular mass PEO (5×10⁵, 2×10⁶) was more obvious, but it would reduce the spreading area of droplets on the leaf surface. Low mass fraction (0.005%, 0.02%) of AOT additives could increased the spreading area of droplets on the leaf surface, reduced the droplet pop-up height and wet the local impact area, but at high impact velocities (v>1.66m/s), the droplets would break multiple satellite droplets and eject from the leaf surface during contraction. At increasing the AOT mass fraction at 0.1%, the droplets were able to wet the leaf surface at the spreading stage and spread to a larger area in a short time. A mixture of droplets using both PEO and AOT additives combining the advantages of polymers and surfactants, was capable of forming filaments that draw drew droplets in the localized wetted areas, enhancing the effective deposition of droplets on the leaf surface. By compiling and analyzing the experimental data, it was found that droplets were more likely to be deposited on the leaf surface by increasing the Weber number (We) while decreasing the Reynolds number (Re).

Key words: superhydrophobic, surfactants, polymers, viscosity, deposition

摘要：

利用高速摄像机拍摄去离子水液滴、3种相对分子质量的聚氧化乙烯（polyethylene oxide，PEO）液滴、表面活性剂硫酸钠琥珀酸二辛酯[bis(2-ethylhexyl)sulfosuccinate，AOT]液滴和两种助剂组合液滴撞击荷叶表面，对比分析不同特性液滴在叶面上的沉积特性。实验结果表明：PEO助剂能够明显抑制液滴反弹和增加液滴在叶面停留时间，阻止向外发射卫星液滴，高相对分子质量PEO（5×10⁵、2×10⁶）抑制效果更加明显，但会降低液滴在叶面上的铺展面积；低质量分数（0.005%、0.02%）的AOT助剂能够增加液滴在叶面上的铺展面积，减小液滴弹起高度，润湿局部撞击区域，但是在撞击速度较高（v>1.66m/s）时，液滴会在收缩时破碎多个卫星液滴而弹离叶面；增加AOT质量分数为0.1%时，液滴能够在铺展阶段润湿叶面，并在短时间内扩散到更大面积；采用PEO和AOT两种助剂的混合液滴结合了聚合物和表面活性剂的优点，能够在局部润湿区域形成牵扯液滴的液丝，增强了液滴在叶面上的有效沉积；通过对实验数据整理分析，发现液滴在降低雷诺数（Re）的同时，提高韦伯数（We）更容易在叶面沉积。

关键词: 超疏水, 表面活性剂, 聚合物, 黏度, 沉积