The pair potential of colloidal stars

TL;DR

This paper introduces colloidal stars composed of polystyrene beads grafted with filamentous viruses, measuring their pair interactions experimentally and comparing results with theoretical models based on counterion osmotic pressure.

Contribution

It presents the first experimental measurement of pair potentials of colloidal stars and validates theoretical predictions using umbrella sampling techniques.

Findings

Interaction potentials depend on ionic strength and grafting density.

Measured interactions agree well with osmotic pressure-based theoretical models.

Experimental method adapts umbrella sampling for colloidal systems.

Abstract

We report on the construction of colloidal stars: 1 micrometer polystyrene beads grafted with a dense brush of 1 micrometer long and 10 nm wide semi-flexible filamentous viruses. The pair interaction potentials of colloidal stars are measured using an experimental implementation of umbrella sampling, a technique originally developed in computer simulations in order to probe rare events. The influence of ionic strength and grafting density on the interaction is measured. Good agreements are found between the measured interactions and theoretical predictions based upon the osmotic pressure of counterions.