Parallel cracks from a desiccating colloidal layer under gravity flow and their use in fabricating metal micro-patterns

Abstract

Desiccating cracks in random networks have been gaining importance as templates for metal deposition to produce conducting meshes, the latter serving as see-through electrode when supported on a transparent substrate. The method being essentially lithography-free, a control over crack formation would simply translate to desirable properties in the patterned meshes. Making cracks parallel among themselves as against random, is clearly a step forward in this direction. Herein, we report a simple, instrument-free scalable technique to produce parallel crack patterns in the desiccating layer using film thickness gradient formed under gravity flow of a colloidal dispersion on an inclined substrate. While the gravity flow defines the thickness gradient, the resultant drying front dictates the orientations of the cracks. The experimental parameters controlling crack width, periodicity and interconnectivity have been explored by varying substrate inclination angle and the drying temperature. Finally as an example of patterning in desired regions, laser printed stripes on PET have been employed to produce confined geometry thereby leading stripes of parallel grating structures.