Effects of surface chemistry and groove geometry on wetting characteristics and droplet motion of water condensate on surfaces with rectangular microgrooves

The study of the wetting characteristics and motion of condensed droplets is important in any multiphase flow applications. The present work focuses on condensate morphology and growth on cooled horizontal substrates featuring microgrooves. Microfabrication techniques are employed to produce chemically homogeneous and heterogeneous substrates with microgrooves 20-40 μm in spacing and 20-180 μm in depth. Strong anisotropic wetting behavior was observed on the chemically heterogeneous sample whereas isotropic wetting appeared on the homogeneous samples. Groove geometry is found to have a profound impact on the drainage behavior of condensed droplets but is less important for deposited droplets. Isolated drop growth in microgrooves was simulated numerically to study various wetting modes. The simulation results show that the critical volume for droplets to change morphology decreases with the increase in the contact angle of surface materials in chemically homogeneous grooves. The critical volume for droplets on the chemical heterogeneous sample is much smaller than those on the homogeneous surfaces.