Drift-free atomic force microscopy measurements of cell height and mechanical properties

Atomic force microscopy (AFM) is used to study the morphological and mechanical properties of living cells. However, experiments performed over minutes to hours are subject to significant instrumental drift. The main sources of drift are the cantilever's geometrical asymmetry and bimorphic construction. We developed a simple software Stick-and-Move (SaM) routine for AFM that eliminates drift by continuously referencing the sample position to the substrate while acquiring force-distance curves. Control experiments show no drift over 15 min at an acquisition rate of 0.1 Hz. As a proof of concept, we applied the SaM to study the response of rat astrocytes to osmotic stress, observing dimensional and constitutive changes during volume regulation.