Chemically induced oscillations in a pH-responsive hydrogel

A Landolt pH-oscillator based on a bromate/sulfite/ferrocyanide reaction has been developed with a room temperature period of 20 min and a range of 3.1 ≤ pH ≤ 7.0. This system has been used to drive periodic oscillations in volume in a pH responsive hydrogel. The gel is coupled to the reaction and changes volume by a factor of at least 6. A continuously stirred, constant volume, tank reactor was set-up on an optical microscope and the reaction pH and gel size monitored.