Effect of Surface Wettability on Crack Dynamics and Morphology of Colloidal Films
- Publication date
- Publisher
Abstract
The
effect of surface wettability on the dynamics of crack formation
and their characteristics are examined during the drying of aqueous
colloidal droplets (1 μL volume) containing nanoparticles (53
nm mean particle diameter, 1 w/w %). Thin colloidal films, formed
during drying, rupture as a result of the evaporation-induced capillary
pressure and exhibit microscopic cracks. The crack initiation and
propagation velocity as well as the number of cracks are experimentally
evaluated for substrates of varying wettability and correlated to
their wetting nature. Atomic force and scanning electron microscopy
are used to examine the region in the proximity of the crack including
the particle arrangements near the fracture zone. The altered substrate–particle
Derjaguin–Landau–Verwey–Overbeek (DLVO) interactions, as a consequence of the changed wettability,
are theoretically evaluated and found to be consistent with the experimental
observations. The resistance of the film to cracking is found to depend
significantly on the substrate surface energy and quantified by the
critical stress intensity factor, evaluated by analyzing images obtained
from confocal microscopy. The results indicate the possibility of
controlling crack dynamics and morphology by tuning the substrate
wettability