Droplets motion on chemically/topographically heterogeneous surfaces

We present a numerical study of droplets sliding across chemically heterogeneous surfaces formed by a periodic pattern of alternating hydrophobic and hydrophilic stripes, or topographically heterogeneous surfaces which are microgrooved. The numerical simulation performed by using a particle-based numerical method, Many-body Dissipative Particle Dynamics (MDPD), is adopted to observe the stick-slip motion of droplets driven by a constant body force. The fractions of two types of surfaces are varied from 0.3 to 0.7 to investigate their influence on stick-slip motion of droplets. The dynamic contact angles and the variation in distance D-fr between the front and the rear contact points are shown for different fractions. The jerky motion characterised by stick-slip motion can be found on chemically heterogeneous surfaces for all fractions we choose and the partial stick-slip motion can also be discovered on topographically heterogeneous surfaces except for fraction phi(s)=0.3. The snapshots of droplet show that stick-slip motion is the consequence of the periodic deformation of droplet interface during crossing heterogeneous surfaces and can be controlled by fractions.