Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA.
Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA.
J Colloid Interface Sci. 2018 Jan 1;509:422-431. doi: 10.1016/j.jcis.2017.09.030. Epub 2017 Sep 8.
Impacting on a superhydrophobic surface, water droplet spreads to a pancake shape and then retracts and bounces off. Although the collision time is mostly in the order of couple of 10ms for millimetric droplets, researchers have shown recently that decorating the superhydrophobic surface with a single macrotexture or intersecting ridge reduces this contact time if the droplet hits the texture or the intersection exactly in the center. Hence, covering the surface with ridges should address this hitting point restriction.
Using an extruder-type 3D printer, we fabricated a superhydrophobic surface fully decorated with cylindrical ridges. The dynamic of water droplet impact on this surface at different impact velocities has been studied for varied droplet volumes and ridge sizes.
Our data show that regardless of the location of the contact point, when the kinetic energy of the drop is sufficient to completely wet the ridges, the contact time reduces ∼13% as the consequence of ∼20% faster retraction. For higher impact velocity, the contact becomes shorter since the flattened drop splashes from the periphery. Moreover, the simplified, time-efficient and inexpensive method of fabricating the surfaces presented in this paper can be implemented in fabricating many versatile superhydrophobic surfaces with complex geometries.
当液滴冲击超疏水表面时，它会扩展成饼状，然后回缩并弹开。尽管对于毫米级的液滴来说，碰撞时间大多在几十毫秒的量级，但最近的研究表明，如果液滴恰好击中纹理或交叉脊的中心，用单个宏观纹理或交叉脊来修饰超疏水表面可以减少这种接触时间。因此，用脊覆盖表面应该可以解决这个撞击点的限制。
我们使用挤出式 3D 打印机制造了一个完全覆盖有圆柱形脊的超疏水表面。研究了不同液滴体积和脊尺寸下，液滴以不同冲击速度冲击该表面的动力学。
我们的数据表明，无论接触点的位置如何，当液滴的动能足以完全润湿脊时，接触时间会减少约 13%，这是由于回缩速度加快了约 20%。对于更高的冲击速度，接触时间会缩短，因为压扁的液滴会从边缘飞溅出来。此外，本文提出的制造表面的简化、高效和低成本方法可以用于制造具有复杂几何形状的许多多功能超疏水表面。
