Adhesive turned on and off

. Teams from the University of Sheffield, the University of Bayreuth in Germany and the Rutherford Appleton Laboratory in Oxford, say the glue loses and regains its stickiness at different pH levels. The glue is made up of polyelectrolytes – polymers that are electrically charged and can change their shape in response to their environment. A polyelectrolyte can stretch out at one pH level, or roll into a ball at another pH. The researchers, led by Mark Geoghegan in the Department of Physics and Astronomy at Sheffield University, showed that if oppositely charged polyelectrolytes are brought together in water they stick tightly. This was widely known, but until now the strength of this bond – and the fact that the process can be reversed and repeated – was not understood.