Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
Langmuir. 2012 Sep 18;28(37):13137-42. doi: 10.1021/la302551m. Epub 2012 Sep 7.
The typically elongated shape of droplets on chemically microstriped surfaces has been suggested to depend strongly on the kinetics during deposition. Here, we unequivocally establish the importance of impact kinetics by comparing the geometry of pico- to microliter droplets deposited from an inkjet nozzle with those obtained by conventional deposition from a syringe. For large Weber numbers, the strongly enhanced spreading during the impact in combination with direction-dependent pinning of the contact line gives rise to more spherical droplets with a low aspect ratio. The impact energy can be minimized by the prolonged firing of small picoliter droplets to form larger droplets or, as shown in the past, by using high-viscosity liquids. In the first case, the impact energy is absorbed by the liquid already present, therewith reducing the impact diameter and consequently forming markedly more elongated droplets.
在化学微条纹表面上，液滴的典型拉长形状被认为强烈依赖于沉积过程中的动力学。在这里，我们通过比较从喷墨喷嘴沉积的皮升到微升液滴的几何形状与通过传统注射器沉积获得的那些液滴，明确地确定了冲击动力学的重要性。对于大韦伯数，冲击过程中强烈增强的扩展以及接触线的方向相关固定导致具有低纵横比的更球形的液滴。可以通过延长小皮升液滴的发射时间来形成更大的液滴，或者如过去所示，通过使用高粘度液体来最小化冲击能量。在前一种情况下，冲击能量被已经存在的液体吸收，从而减小了冲击直径，从而形成明显更拉长的液滴。
