Room-temperature ice films

Room-temperature ice films can be made if water is confined and subjected to a modest electric field. Simulations have shown that strong fields of around 10⁹ V/m can align water dipoles and crystallize them into polar cubic ice. In the new work, done in the lab of Heon Kang at Seoul National University in Korea, scientists examined the properties of room-temperature water in the gap between a gold substrate and the gold tip of a scanning tunneling microscope. They saw a sudden phase transition from liquid to solid when two conditions were met: when the gap shrank to a critical value of 7 Å and when the imposed electric field was at least a few times 10⁶ V/m. Noting that the field is far too weak to polarize water, the researchers think they have found a new type of freezing transition. They also note that comparable field strengths are found, for example, within ion channels in biological cells, at the charged interfaces of proteins and nanodevices, and in thunder-clouds. (E.-M. Choi et al., Phys. Rev. Lett. 95 , 085701, 2005 http://dx.doi.org/10.1103/PhysRevLett.95.085701 .)