Micrometer scale adhesion on nanometer-scale patchy surfaces: adhesion rates, adhesion thresholds, and...

Area of Science:

• Colloid and Surface Science
• Electrostatics
• Materials Science

Background:

• Understanding particle-surface interactions is crucial in fields like materials science and nanotechnology.
• Electrostatic interactions govern adhesion, especially in aqueous dispersions.
• Patchy surfaces, with localized attractive regions on a repulsive background, present complex interaction scenarios.

Purpose of the Study:

• To investigate the adhesion rates of spherical particles onto patchy planar surfaces.
• To determine the influence of attractive patch density, particle size, and ionic strength on adhesion.
• To identify and characterize an adhesion threshold for particle capture.

Main Methods:

• Experimental measurements of particle adhesion rates from flowing dispersions onto engineered silica surfaces.
• Systematic variation of surface patch loading, particle diameter (0.5 and 1 µm), and ionic strength.
• Theoretical analysis of lengthscales governing adhesion and comparison with experimental observations.

Main Results:

• High surface patch density leads to maximum (transport-limited) particle adhesion rates.
• Low surface patch density exhibits an adhesion threshold, a critical patch density required for particle capture.
• Adhesion rates at low densities are dependent on particle size, ionic strength, and patch distribution, indicating selective adhesion.

Conclusions:

• An adhesion threshold exists for patchy surfaces, governed by the interplay of patch arrangement and particle properties.
• This threshold allows patchy surfaces to selectively capture particles based on size and other physical characteristics.
• The findings have implications for designing surfaces with controlled adhesion properties and understanding colloidal self-assembly.