Howland Christopher J, Antkowiak Arnaud, Castrejón-Pita J Rafael, Howison Sam D, Oliver James M, Style Robert W, Castrejón-Pita Alfonso A
Trinity College, University of Oxford, Oxford OX1 3BH, United Kingdom.
Institut Jean Le Rond d'Alembert, UMR 7190 CNRS/UPMC, Sorbonne Universités, F-75005 Paris, France.
Phys Rev Lett. 2016 Oct 28;117(18):184502. doi: 10.1103/PhysRevLett.117.184502. Epub 2016 Oct 26.
Droplets splash when they impact dry, flat substrates above a critical velocity that depends on parameters such as droplet size, viscosity, and air pressure. By imaging ethanol drops impacting silicone gels of different stiffnesses, we show that substrate stiffness also affects the splashing threshold. Splashing is reduced or even eliminated: droplets on the softest substrates need over 70% more kinetic energy to splash than they do on rigid substrates. We show that this is due to energy losses caused by deformations of soft substrates during the first few microseconds of impact. We find that solids with Young's moduli ≲100 kPa reduce splashing, in agreement with simple scaling arguments. Thus, materials like soft gels and elastomers can be used as simple coatings for effective splash prevention. Soft substrates also serve as a useful system for testing splash-formation theories and sheet-ejection mechanisms, as they allow the characteristics of ejection sheets to be controlled independently of the bulk impact dynamics of droplets.
当液滴以高于临界速度撞击干燥、平坦的基底时会溅起水花，临界速度取决于液滴大小、粘度和气压等参数。通过对撞击不同硬度硅胶的乙醇液滴进行成像，我们发现基底硬度也会影响溅起阈值。溅起现象会减少甚至消除：在最软基底上的液滴比在刚性基底上的液滴溅起所需的动能要多70%以上。我们表明这是由于在撞击的最初几微秒内软基底变形导致的能量损失。我们发现杨氏模量≲100 kPa的固体可减少溅起，这与简单的比例论证一致。因此，像软凝胶和弹性体这样的材料可用作有效的防溅简单涂层。软基底还可作为测试溅起形成理论和薄片喷射机制的有用系统，因为它们能使喷射薄片的特性独立于液滴的整体撞击动力学进行控制。
