# Capillary force on a tilted cylinder: AFM measurements

## TL;DR

This study measures how capillary forces on a tilted cylinder vary with angle using AFM, confirming a theoretical model and discussing measurement accuracy for surface tension and contact angle.

## Contribution

It introduces a method to measure capillary forces on tilted cylinders with AFM, validating a 1/cos i dependence and addressing torque correction effects.

## Key findings

- Capillary force varies as 1/ cos i with tilt angle.
- Torque correction is essential for accurate measurements.
- Method can estimate surface tension times cosine of contact angle.

## Abstract

We investigate the capillary force that applies on a tilted cylinder as a function of its dipping angle i, using a home-built tilting Atomic Force Microscope (AFM) with custom made probes. A micrometric-size rod is glued at the end of an AFM cantilever of known stiffness, whose deflection is measured when the cylindrical probe is dipped in and retracted from reference liquids. We show that a torque correction is necessary to understand the measured deflection. The results are compatible with a vertical capillary force varying as 1/ cos i, in agreement with a recent theoretical prediction. We also discuss the accuracy of the method for measuring the surface tension times the cosine of the contact angle of the liquid on the hanging fiber.