Ever since the 1970s, scientists have been trying to establish the cause of a repulsive force occurring between different electrostatically charged molecules, such as DNA and other biomolecules, when they are very close to each other in aqueous media. This force became know as hydration force.
Jordi Faraudo, a researcher for the Department of Physics at the Universitat Autònoma de Barcelona, and Fernando Bresme of the Department of Chemistry at Imperial College London have studied this mysterious force in detail and have discovered where its origins lie.
In the same way that a flag flutters in the direction the wind is blowing, at a microscopic level water molecules are gently attracted towards the direction in which an electric field is pointing. However, when the water is in contact with surfaces that create small electric fields, such as chemical compounds like those found in many detergents, this is no longer the case: the water molecules have a remarkable capacity to organise themselves into complex structures that are strongly orientated in such a way as to cancel out the electric field, and on some occasions, to reverse it. This abnormal behaviour was discovered by the same researchers and published in Physical Review Letters in April 2004.