The measurement of van der Waals forces between two-dimensional materials and multilayer stacks in air and water

Two-dimensional materials have a prime interest for applications in materials, chemistry, and biology, as possessing unique one atom thickness with extended lateral dimensions. Since many applications rely on interfacial stacking of 2D materials, understanding interactions between 2D sheets and in their multilayer stacks is of paramount importance. Our experimental strategy enables rapid and high-throughput experimental determination of forces between 2D materials both in air and in liquids using atomic force spectroscopy. We found that measured scaling of the van der Waals force as a function of separation distance substantially differs from theoretical predictions and depends on the number of layers. Conducted experiments in deionized water showed repulsive forces between two hydrophobic surfaces, which differ at higher ionic strength. Our experiments provide a new experimental strategy and much needed knowledge for the further development of van der Waals methodologies.