Global consequences of a local Casimir force: Adhered cantilever

TL;DR

This paper explores how the shape of adhered cantilevers can reveal information about surface adhesion and dispersion forces, offering a new method to measure these forces at short separations.

Contribution

It demonstrates that adhered cantilevers are sensitive to dispersion forces and can be used to measure these forces separately from adhesion energy.

Findings

The shape of adhered cantilevers encodes information about dispersion forces.

Dispersion forces significantly influence cantilever shape near contact point.

Adhered cantilevers can measure dispersion forces where other methods fail.

Abstract

Although stiction is a cumbersome problem for microsystems, it stimulates investigations of surface adhesion. In fact, the shape of an adhered cantilever carries information of the adhesion energy that locks one end to the substrate. We demonstrate here that the system is also sensitive to the dispersion forces that are operative very close to the point of contact, but their contribution to the shape is maximum at about one third of the unadhered length. When the force exceeds a critical value the cantilever does not lose stability but it settles at smaller unadhered length, whose relation to adhesion energy is only slightly affected by the force. Our calculations suggest to use adhered cantilevers to measure the dispersion forces at short separations, where other methods suffer from jump-to-contact instability. Simultaneous measurement of the force and adhesion energy allows the separation of the dispersion contribution to the surface adhesion.