Nanoscale wetting of viruses by ionic liquids

Abstract

One of the most important effects of water on earth is that surfaces in air adsorb small amounts ofwater, usually in the form of a thin film. Real surfaces, especially the rather soft biomolecular surfaces, are covered by highly curved micro- and nanostructures, which induce more complex wetting geometries, such as films, droplets, and filaments. This effect, though ubiquitous, has not yet been investigated on the nanoscale. We have approached the situation by combining a soft proteinous surface, made up from very resilient tubular plant viruses, with ionic liquids. Their low vapor pressure allowed us to observe nanoscale wetting patterns at very high spatial resolution with AFM (atomic force microscopy), SEM (scanning electron microscopy) and STEM (scanning transmission electronmicroscopy).We found droplets, filaments and layers,withmeniscus diameters down to below10 nm. All geometries are comparablewith results obtained on the microscale, and with standard macroscale wetting models.