Roughness induced rotational slowdown near the colloidal glass transition.

Area of Science:

• Colloid and Surface Science
• Soft Matter Physics
• Materials Science

Background:

• Colloid dynamics in concentrated suspensions are heavily influenced by particle shape and surface topography.
• Surface roughness affects translational and rotational Brownian motion differently as particles approach each other.
• Geometric hindrance from interacting asperities can frustrate particle rotations.

Purpose of the Study:

• To investigate the effect of surface roughness on the translational and rotational dynamics of model raspberry-like colloids.
• To analyze how varying concentrations impact these dynamics up to the maximum packing fraction.

Main Methods:

• Utilized model raspberry-like colloids to examine roughness effects.
• Employed Confocal Scanning Laser Microscopy and particle tracking.
• Simultaneously resolved translational and rotational Brownian motion to obtain Mean Squared Displacements.

Main Results:

• Surface roughness lowers the concentration for the translational colloidal glass transition.
• A concentration-dependent shift in rotational Brownian motion from diffusive to rattling behavior was observed.
• A second glass transition for rough spherical colloids emerges when intersurface distance approaches the roughness length scale.

Conclusions:

• Surface characteristics significantly alter rotational dynamics during colloidal glass formation.
• This study provides a unifying understanding of roughness effects on colloidal motion.
• The findings offer a microscopic basis for understanding roughness-related phenomena in natural and technological systems.