标题： 非融合和平面内动量生成在驻留液滴簇中 显示英文标题

标题： Non-coalescence and in-plane momentum generation in sessile droplet clusters

摘要： 直观上，当接近的液滴接触时会合并。 然而，在某些条件下，由于中间气体薄膜的夹带，它们可能不会融合。 到目前为止，水滴之间的不融合现象是在水滴以相对质心速度运动时的碰撞中观察到的，或者在存在特定促进效应的情况下，如高介入气体压力、表面活性剂或大尺寸液滴（直径$\gtrsim 1~\mathrm{mm}$）的情况下观察到。 在这里，我们在更宽的液滴直径范围内，从毫米级到小至100微米，无需上述任何因素即可观察到水滴之间的不融合。 这种不融合发生在疏水表面上的静置液滴簇中。 当簇中的任何两个液滴融合时，融合液滴的演变界面似乎与簇中的其他相邻液滴接触，但不一定触发进一步的融合。 事实上，这种看似接触可以表现为弹跳相互作用，并且根据液滴的初始几何排列，它可以产生显著的横向动量，从而导致参与液滴的自发平面内自推进。 该过程的能量转换效率对于紧密排列的三个静置液滴簇高达9%，并且随着参与液滴数量的增加而进一步提高。 这种小液滴的自推进揭示了在超疏水表面上滴状冷凝过程中被动液滴去除和表面更新的新途径，在多种应用中至关重要。 显示英文摘要

摘要： Intuitively, droplets in proximity merge when brought into contact. However, under certain conditions, they may not coalesce due to the entrapment of an interstitial gas film. Non-coalescence between water droplets has so far been observed during collisions of droplets moving with relative centroidal velocity, or in the presence of specific enabling effects such as high intervening gas pressures, surfactants, or large droplet sizes (diameter $\gtrsim 1~\mathrm{mm}$). Here, we report non-coalescence between water droplets over a much wider range of droplet diameters, from millimeters to as small as 100 microns, without the need for any of the above factors. Such non-coalescence occurs in sessile droplet clusters on water-repellent surfaces. When any two droplets in a cluster coalesce, the evolving interface of the coalescing droplets comes in apparent contact with other neighbouring droplets in the cluster, but does not necessarily trigger further coalescence. In fact, such apparent contact can manifest as a bouncing interaction, and depending on the initial geometric arrangement of droplets, it can result in significant lateral momentum generation, consequently leading to spontaneous in-plane self-propulsion of the participating droplets. The energy conversion efficiency of this process reaches as high as 9\% for closely packed clusters of three sessile droplets and increases further with an increase in the number of participating droplets. The resulting self-propulsion of such small droplets reveals a new pathway for passive droplet removal and surface renewal during dropwise condensation on superhydrophobic surfaces, critical in multiple applications.