How surface functional groups influence fracturation in nanofluid droplet dry-outs

Area of Science:

• Materials Science
• Fluid Dynamics
• Surface Chemistry

Background:

• Drying of colloidal droplets is crucial in various applications.
• Understanding crack formation in drying films is essential for material design.

Purpose of the Study:

• To investigate the impact of surface functional groups and substrate surface energies on crack formation and dry-out shape in drying water-based nanofluid droplets.
• To establish relationships between material properties, drying behavior, and resulting deposit morphology.

Main Methods:

• Drying experiments were conducted using water-based nanofluids with polystyrene nanoparticles functionalized with various groups.
• Nanofluids were dried on substrates with differing surface energies.
• Crack patterns and dry-out shapes were analyzed to correlate with surface properties.

Main Results:

• A variety of regular crack patterns were observed under controlled conditions.
• The crack spacing to deposit height ratio remained constant for similar substrate surface energies and increased linearly with surface energy.
• Surface functional groups significantly influenced crack shape due to altered particle interactions and compaction during drying.

Conclusions:

• Substrate surface energy and nanoparticle surface functional groups are critical determinants of crack formation and morphology in drying nanofluid droplets.
• The findings provide insights into controlling the drying process and the resulting structures of functional nanomaterials.