液滴碰撞亲-疏水交界面的动力学特征

Dynamic Characteristic of Droplet Collision at Hydrophilic-hydrophobic Interface

液滴碰撞不同润湿性表面将表现出不同的动态行为。为研究液滴碰撞亲-疏水交界面的动态行为,制备了超疏水-超亲水组合润湿性表面,控制液滴(初始直径D 0为1.80 mm)以不同速度碰撞超亲水-超疏水交界面。研究结果表明:液滴轻触交界面时,相邻两极端润湿性表面将产生促使液滴铺展的驱动力,液滴在超亲水区域完全铺展,最大铺展直径可达5.51 mm,铺展系数β可达2.93。液滴以一定速度碰撞亲-疏水交界面时,液滴铺展和液滴弹跳同时发生。液滴铺展系数先增大后骤降,铺展系数曲线存在“尖峰”。最终铺展系数逐渐增大并趋于稳定。碰撞速度越大,铺展前期铺展系数越大。对液滴铺展过程中的能量分析表明,液滴动能和表面能的相互转换是液滴运动和铺展的关键。

Droplet collision with different wettability surfaces will exhibit different dynamic behaviors.To study the dynamic behavior of droplets collision at the hydrophilic-hydrophobic interface,a superhydrophilic-superhydrophobic hybrid wettability surface was prepared.The droplets(the initial diameter D 0 is 1.80 mm)were controlled to collide on the superhydrophilic-superhydrophobic interface at different speeds.The results show that when the droplets collide with the hydrophilic-hydrophobic interface,the adjacent two extreme wettability surfaces will generate the driving force for droplet spreading.And the droplets will spread completely in the superhydrophilic region.The maximum spreading diameter can reach 5.51 mm and the droplet spreading coefficientβcan be up to 2.93.When the droplet collides with the hydrophilic-hydrophobic interface at a certain speed,the droplet spreading and the droplet bounce occur simultaneously.The droplet spreading coefficient first increases,then decreases,and there is a“spike”in the spreading coefficient curve.The final spreading coefficient gradually increases and tends to be stable.The greater the impact speed,the larger the spreading coefficient in the early stage of spreading.The energy analysis during the droplet spreading process shows that the mutual conversion of droplet kinetic energy and surface energy is the key to droplet motion and spreading.