The team, led by Professor Rahul Nair, embedded conductive filaments within the electrically insulating graphene oxide membrane. An electric current passed through these nano-filaments created a large electric field which ionises the water molecules and thus controls the water transport through the graphene capillaries in the membrane.
Prof Nair said: “Developing smart membranes that allow precise and reversible control of molecular permeation using external stimuli would be of intense interest for many areas of science; from physics and chemistry, to life-sciences. “
According to the researchers, this achievement is a step change because of its similarity to several biological processes where the main stimuli are electrical signals. Controlled water transport is key for renal water conservation, regulation of body temperature and digestion. Therefore, it can be used to develop artificial biological systems and advanced nanofluidic devices for various applications.
Previously, the research group has demonstrated that graphene oxide membranes can be used as a sieve to remove salt from seawater for desalination alternatives. Last year they also showed that the membranes could remove the colour pigment from whisky without affecting its other properties.
Dr Kai-Ge Zhou, lead researched on the project said: “The reported graphene smart membrane technology is not just limited to controlling the water flow. The same membrane can be used as a smart adsorbent or sponge. Water adsorbed on the membrane can be preserved in the membrane even in desert conditions if a current is applied. We could release this water on demand by switching the current off.”
The University of Manchester is preparing to open the £60m Graphene Engineering Innovation Centre (GEIC) to complement the NGI. The GEIC will provide scale-up of the membranes and pilot-scale testing capability.
