Synergy between the crack pattern and substrate elasticity in colloidal deposits.

Area of Science:

• Materials Science
• Soft Matter Physics
• Surface Science

Background:

• Desiccation cracks form in colloidal deposits to relieve strain energy from drying-induced shrinkage and substrate adhesion.
• Crack morphology is influenced by material properties and substrate interactions.

Purpose of the Study:

• To investigate the effect of substrate elasticity on the morphology of desiccation cracks in colloidal deposits.
• To understand the correlation between substrate elasticity and crack pattern formation.

Main Methods:

• Experiments involving sessile drops of colloidal suspensions on elastomer (soft) and glass (stiff) substrates.
• Analysis of crack patterns using microscopy and mechanical property measurements.
• Theoretical calculations to correlate crack morphology with substrate elasticity.

Main Results:

• Distinct crack morphologies were observed: radial cracks on stiff substrates and circular cracks on soft substrates.
• The difference in crack patterns is solely attributed to the elasticity of the underlying substrates.
• A significant alteration in energy release rates during crack nucleation and propagation was found due to the elastic mismatch.

Conclusions:

• Substrate elasticity is a critical factor controlling desiccation crack morphology in colloidal deposits.
• The transition from radial to circular cracks is governed by the substrate's elastic modulus, influencing in-plane stresses.
• Understanding this relationship is key for controlling crack formation in thin film deposition and material design.