Graphene has proven itself as not only a great conductor for heat and electricity, but also a perfect substance for a barrier film and bullet repellent. However, researchers from MIT, Oak Ridge National Laboratory, have discovered that although the material seems impenetrable, by building large membranes from single sheets of graphene grown by chemical vapour deposition, small molecules of salts could pass through.
The team does not intend to find limitations in the use of the material. Just the opposite, by conducting this experiment, they were able to find additional applications particularly in the field of microbiology. The study was just published in the journal ACS Nano.
Rohit Karnik, associate professor of mechanical engineering at MIT, is certain that there are many chemical methods that have not been applied yet and can be used to change and explore the membranes.
Sean O’Hern, the graduate student under the supervision of Karnik, looked for leaps in the membrane performance. The membranes should not only filter fluids quickly, but they should also be easily to tailor so that some molecules could be let through while others are trapped. Graphene was chosen because it has thin structure and at the same time it is very strong.
The team created a 25 square millimeters membrane that contains around a quadrillion carbon atoms. With the help of Jing Kong, the ITT Career Development Associate Professor of Electrical Engineering at MIT, they managed to synthesize graphene by chemical vapor, and then transferred the sheet to a polycarbonate substrate dotted with holes.
Karnik’s research group conducted two additional tests. One used copper foil with graphene grown on it. They exposed it to chemical agent, which happened to pass through. Another conclusion from this was that there is a limit to the size of the pores letting through only small molecules. The second experiment involved close observation of the material using a high-powered electron microscope, which allowed measuring the exact size of the pores.
The scientists believe that these newly discovered membranes could be used in various aspects of drug delivery or a included in a portable sensor to protect it from the environment and letting only certain elements through. The research is still ongoing, now directed towards water filtration.