Line tension and its influence on droplets and particles at surfaces

In this review we examine the influence of the line tension tau on droplets and particles at surfaces. The line tension influences the nucleation behavior and contact angle of liquid droplets at both liquid and solid surfaces and alters the attachment energetics of solid particles to liquid surfaces. Many factors, occurring over a wide range of length scales, contribute to the line tension. On atomic scales, atomic rearrangements and reorientations of submolecular components give rise to an atomic line tension contribution T-atom (similar to 1 nN), which depends on the similarity/dissimilarity of the droplet/particle surface composition compared with the surface upon which it resides. At nanometer length scales, an integration over the van der Waals interfacial potential gives rise to a mesoscale contribution vertical bar tau(vdw)vertical bar similar to 1-100 pN while, at millimeter length scales, the gravitational potential provides a gravitational contribution tau(grav)similar to+1-10 N. tau(grav) is always positive, whereas, twaq can have either sign. Near wetting, for very small contact angle droplets, a negative line tension may give rise to a contact line instability. We examine these and other issues in this review. (C) 2016 Elsevier Ltd. All rights reserved.