Three-dimensional quantitative force maps in liquid with 10 piconewton, angstrom and sub-minute resolutions

Abstract

We develop a bimodal force microscopy method to map the three-dimensional force fields and their time-evolution on a variety of solid-water interfaces. The force maps show an oscillatory decaying force perpendicular to the solid surface with a 0.3 nm periodicity. The technique enables the three-dimensional imaging and mapping of the hydration layers and forces on mica and protein GroEL surfaces with 10 piconewton, 2 angstrom and 40 second (whole volume) resolutions. We record the existence and evolution of nanoscale perturbations involving thousands of water molecules of the protein-liquid interface. Those instabilities are not found in stiff and atomically flat interfaces.