Effect of particle polydispersity on the irreversible adsorption of fine particles on patterned substrates

TL;DR

This study uses Monte Carlo simulations to analyze how particle size variation influences the irreversible adsorption of polydisperse particles on patterned substrates, revealing size-dependent phase behavior and preferential adsorption of smaller particles.

Contribution

It extends previous models by incorporating size dispersion effects into the adsorption process on patterned substrates, highlighting the role of particle size extremes in phase transitions.

Findings

Transition depends on largest and smallest particle sizes

Coverage varies non-monotonically with cell size

Smaller particles preferentially adsorb at high polydispersity

Abstract

We performed extensive Monte Carlo simulations of the irreversible adsorption of polydispersed disks inside the cells of a patterned substrate. The model captures relevant features of the irreversible adsorption of spherical colloidal particles on patterned substrates. The pattern consists of (equal) square cells, where adsorption can take place, centered at the vertices of a square lattice. Two independent, dimensionless parameters are required to control the geometry of the pattern, namely, the cell size and cell-cell distance, measured in terms of the average particle diameter. However, to describe the phase diagram, two additional dimensionless parameters, the minimum and maximum particle radii are also required. We find that the transition between any two adjacent regions of the phase diagram solely depends on the largest and smallest particle sizes, but not on the shape of the distribution function of the radii. We consider size dispersions up-to 20% of the average radius using a physically motivated truncated Gaussian-size distribution, and focus on the regime where adsorbing particles do not interact with those previously adsorbed on neighboring cells to characterize the jammed state structure. The study generalizes previous exact relations on monodisperse particles to account for size dispersion. Due to the presence of the pattern, the coverage shows a non-monotonic dependence on the cell size. The pattern also affects the radius of adsorbed particles, where one observes preferential adsorption of smaller radii particularly at high polydispersity.