Sticky switch

Scientists from the University of Sheffield, in collaboration with the University of Bayreuth in Germany and the Rutherford Appleton Laboratory in Oxford, have developed a water-based adhesive that can be turned on and off.

The glue, which can lose and regain its stickiness at different pH levels, could have huge implications for administering drugs in the body.

The glue is made up of polyelectrolytes, which are polymers that are electrically charged and can change their shape in response to their environment. A polyelectrolyte can either stretch out, when at one pH level, or roll into a ball at another pH.

The researchers, led by Dr Mark Geoghegan in the Department of Physics and Astronomy at the University of Sheffield, 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.