Droplet Sliding: The Numerical Observation of Multiple Contact Angle Hysteresis

Abstract

Droplets sliding on surfaces always exhibit an advancing and a receding contact angle. When exerting different driving forces on the droplet to force it to slide at different velocities, the droplet would alter its shape to adapt to the new motion. Hence, different advancing/receding contact angles are likely to be observed, leading to the multiple contact angle hysteresis on a given surface. To verify this hypothesis, many-body dissipative particle dynamics is employed to perform the sliding simulation on both chemically homogeneous and heterogeneous surfaces. By ensuring the droplet sliding in uniform motions under different driving forces, the advancing/receding contact angles are recorded for analysis. Simulation results show that, for homogeneous surfaces, a larger driving force can result in both larger advancing contact angle and smaller receding contact angle, while for heterogeneous surfaces, increasing the driving force only results in smaller receding contact angles. For both cases, multiple contact angle hysteresis can be observed. These observations are contrary to the currently prevailing opinion, which believes that the contact angle hysteresis should be unique on given surfaces. Our findings would advance the understanding of wetting phenomena and possibly inspire new guidance for the design of functional interfaces.

Breaking the symmetry to suppress the Plateau–Rayleigh instability and optimize hydropower utilization

“…5 , Supplementary Discussion 1 . According to the previous result 36 , 40 , 41 , the droplet on the LPW surface is subjected to an unbalanced lateral force F Lat 40 , 41 , which may affect the liquid flow inside the droplet. For clear clarification, we simulate the droplet impact process on these surfaces using the coupled Level-Set and Volume of Fluid (CLSVOF) method (Details see Supplementary Method 2 ).…”

Implementing Contact Angle Hysteresis in Moving Mesh-Based Two-Phase Flow Numerical Simulations

“…However, solid surfaces can hardly be perfectly homogeneous and smooth because most of them are covered with natural defects, rough structures, or artificial patterns, where the apparent contact angle is generally different from the equilibrium CA. 2 − 4 The CA when the interface is moving forward (called the advancing CA) is larger than that when moving backward (called the receding CA). The difference between the advancing CA and the receding CA is defined as contact angle hysteresis (CAH).…”

“…The difference between the advancing CA and the receding CA is defined as contact angle hysteresis (CAH). 1 , 4 − 6 CAH is one of the most common phenomena in nature, which also plays an important role in industrial applications such as immersion lithography, fiber coatings, and inkjet printing. 2 Recently, many digital microfluidics 7 − 9 take advantage of surface wetting phenomena to achieve droplet manipulations and drug delivery.…”

Modified Voronoi Analysis of Spontaneous Formation of Interfacial Droplets on Immersed Oil–Solid Substrates

“…There is a growing interest in the controlled formation of droplets on solid substrates, [1][2][3][4][5][6][7][8] for applications such as the fabrication of microstructured surface, 9,10 controlled condensation, 11,12 cooling 13,14 and fog harvesting. [15][16][17][18] Studies on single or a few droplets have enabled advancements in our understanding of processes such as contact line pinning 19,20 , droplet growth [21][22][23] and coalescence. [24][25][26][27] However, the droplet behavior in realistic systems is controlled by complex many-body interactions and is extremely sensitive to initial conditions, [28][29][30][31] making a statistical analysis via automatic techniques necessary.…”