Advancing liquid contact line on visco-elastic gel substrates: stick-slip vs. continuous motions

Tadashi Kajiya, Adrian Daerr, Tetsuharu Narita, Laurent Royon, François Lequeux, Laurent Limat
2013 Soft Matter  
We studied the dynamics of water sessile droplets advancing on hydrophobic and visco-elastic Poly(styrene-butadiene-styrene)(SBS)-paraffin gel substrates at various inflation rates. During the advancing process, the droplet contact line exhibits three different regimes of motions. When the contact line advances at a high velocity, the contact line moves continuously with a constant contact angle. As the contact line slows down, it starts stick-slip motion: the contact line is pinned at a
more » ... pinned at a certain position, then suddenly slips forward. With further decrease of the velocity, the contact line stops stick-slip and continuously advances again. The observed threshold values for the transitions of the contact line motions (continuous -stick-slip -continuous) indicate that the rheology of the gel drastically affects the dynamics of liquid on its surface. We suggest that on visco-elastic gels, the moving contact line exhibits both aspects of wetting on elastic solids and wetting on viscous liquids depending on the characteristic frequency of the gel surface deformation. At an intermediate regime, the stick-slip motion of the contact line appears. We also propose a simple geometrical model in the stick-slip regime which allows us to relate the jumps of droplet radius to the jumps of apparent contact angle. * Current affiliation is PPMD-SIMM, UMR 7615, CNRS, UPMC, ESPCIParisTech,
doi:10.1039/c2sm26714d fatcat:sjjsejoysvc7dmfrdfvcyd5xku