Weak dispersive forces between glass-gold macroscopic surfaces in alcohols

TL;DR

This study experimentally validates Lifshitz theory predicting weak dispersive van der Waals forces between gold, glass, and alcohols, showing these forces are weaker than in air and generally align with theoretical predictions.

Contribution

First experimental validation of Lifshitz theory for dispersive forces in gold-alcohol-glass systems using atomic force microscopy.

Findings

Dispersive forces are attractive and weaker than in air.

Results are in reasonable agreement with Lifshitz theory.

Addition of salt screens electrostatic forces, isolating dispersive forces.

Abstract

In this work we concentrate on an experimental validation of the Lifshitz theory for van der Waals and Casimir forces in gold-alcohol-glass systems. From this theory weak dispersive forces are predicted when the dielectric properties of the intervening medium become comparable to one of the interacting surfaces. Using inverse colloid probe atomic force microscopy dispersive forces were measured occasionally and under controlled conditions by addition of salt to screen the electrostatic double layer force if present. The dispersive force was found to be attractive, and an order of magnitude weaker than that in air. Although the theoretical description of the forces becomes less precise for these systems even with full knowledge of the dielectric properties, we find still our results in reasonable agreement with Lifshitz theory.