The mechanism by which nanoparticles suspended in liquids self-organize on substrates to ring patterns has attracted much attention, because of a large body of possible practicable applications. Recent work demonstrated that, for example, gravity affects ring geometry, showing that the mechanism of ring formation is indeed not fully understood. Current models suppose that the pinning of the contact line between drops and substrates is a prerequisite for ring formation and that the process is induced either by surface irregularities of the substrate itself, or by self-pinning, triggered by the attachment of suspended material to the substrate. The latter mode was illustrated for drops of aqueous suspensions, evaporating on atomically flat hydrophilic substrates, e.g., freshly cleaved mica. Conversely, the crucial role of pinning on ring formation was derived from the observation that no rings were formed on smooth Teflon. Here we provide the first experimental evidence of the formation of rings on supersmooth hydrophobic surfaces lacking the known conditions required for particle immobilization. Results are suitable to extend existing models and are expected to be instrumental in the predictable design of cell-integrative crystalline ring patterns on biomaterial surfaces and the production of symmetrical ring patterns in proteomics, where the rings are particularly useful to study interaction scenarios between competing proteins.

Current models predict that the elevation of the Earth's surface temperature due to global warming is accompanied by a warming of the troposphere, and a thickening cloud cover associated with longer-lasting clouds, in particular over land. These effects can have an instant impact on the vitality level of microorganisms in clouds and the spreading of airborne diseases. Microorganisms could originate from locations on the Earth, or even arrive from space. Primordial proteins in nanobacteria, only recently identified in the atmosphere, could play a significant role in clouds--accelerating the formation of cloud droplets and interconnecting nanobacteria (and possibly nanobacteria and other microorganisms), thus enhancing their chances to eventually reach the Earth.

Mineralized nanobacteria have been found in a large number of human kidney stones. To analyze the mechanism of the stone formation induced by these crystalline biosystems, we demonstrate how free energy reduction by molecular interface crossing (FERMIC)sa powerful molecular transport mechanism derived from first principlesscould be implemented into existing concepts. FERMIC is generated by thermodynamic instabilities between nanoscopic molecular assemblies at proximal curvature asymmetries and predicts that kidney stones could be formed by material transfer between differently sized nanobacteria in interfacial proximity, immobilized for extended periods within the kidneys. Therapies counteracting kidney stone formation are suggested by the model and include biochemical and physical strategies allowing a reduction of the size differences as well as a minimization of the period of interfacial proximity between the nanobacteria passing the kidneys, principal factors recognized as essential for stone formation.