Nanoscale Topographical Fluctuations: A Key Factor for Evaporative Colloidal Self-Assembly.

Area of Science:

• Materials Science
• Surface Science
• Colloid Science

Background:

• Evaporative self-assembly of colloidal particles is crucial for creating ordered patterns.
• Surface properties like nanoscale roughness influence droplet behavior and deposition patterns.
• Understanding these interactions is key for controlling self-assembly in various applications.

Purpose of the Study:

• To investigate the effect of nanoscale surface parameters (roughness, topography, skewness) on the evaporative self-assembly of colloidal droplets on silicon surfaces.
• To evaluate how varying surface roughness affects droplet contact angle, deposition patterns, crack density, and rim growth.
• To theoretically model the Derjaguin-Landau-Verwey-Overbeek (DLVO) interactions influenced by surface roughness.

Main Methods:

• Experimental evaluation of contact angle, deposition patterns, crack density, and rim growth velocities on silicon surfaces with varying roughness.
• Theoretical calculation of DLVO forces considering large- and small-scale roughness parameters.
• Correlation analysis between surface skewness, asperity radius, DLVO forces, and deposit patterns.

Main Results:

• Rougher silicon surfaces exhibit increased droplet contact angles and rim growth rates compared to smooth surfaces.
• Increased surface roughness reduces stress in drying droplets, leading to decreased crack formation.
• Theoretical DLVO force calculations, considering surface roughness, corroborate experimental findings.

Conclusions:

• Surface nanoscale roughness, topography, and skewness play a critical role in controlling evaporative self-assembly patterns of colloidal droplets.
• Surface roughness influences droplet dynamics and reduces cracking, offering a method to tune self-assembly.
• This study provides insights for selecting appropriate topographic surfaces for specific self-assembly applications.