In a number of recent posts I’ve looked at the ways that nanotechnology coatings like those produced by P2i can be used to make everything from mobile phones to trainers water repellent – and at the natural examples of this same phenomenon – but I haven’t really considered the science behind this technology – which is all about the electromagnetic interaction of molecules. We’re probably most familiar with this kind of interaction in an attractive way. As I write this, there is a heavy frost outside. Water is turning from liquid to solid. Yet were it not for a particular molecular interaction, this would be an impossibility because water would boil below -70 °C. There would be no liquid or solid water on the Earth and, in all probability, no life. The interaction that makes life possible is hydrogen bonding. This is an electromagnetic attraction between a hydrogen atom in one molecule, and an atom like oxygen, nitrogen or fluorine in a second molecule. When hydrogen is bonded