MIT engineers have found a way to directly “pinprick” microscopic holes into graphene as the material is grown in the lab. With this technique, they have fabricated relatively large sheets of graphene (“large,” meaning roughly the size of a postage stamp), with pores that could make filtering certain molecules out of solutions vastly more efficient.
Such holes would typically be considered unwanted defects, but the MIT team has found that defects in graphene — which consists of a single layer of carbon atoms — can be an advantage in fields such as dialysis. Typically, much thicker polymer membranes are used in laboratories to filter out specific molecules from solution, such as proteins, amino acids, chemicals, and salts.
If it could be tailored with pores small enough to let through certain molecules but not others, graphene could substantially improve dialysis membrane technology: The material is incredibly thin, meaning that it would take far less time for small molecules to pass through graphene than through much thicker polymer membranes.
The researchers also found that simply turning down the temperature during the normal process of growing graphene will produce pores in the exact size range as most molecules that dialysis membranes aim to filter. The new technique could thus be easily integrated into any large-scale manufacturing of graphene, such as a roll-to-roll process that the team has previously developed.
“If you take this to a roll-to-roll manufacturing process, it’s a game changer,” says lead author Piran Kidambi, formerly an MIT postdoc and now an assistant professor at Vanderbilt University. “You don’t need anything else. Just reduce the temperature, and we have a fully integrated manufacturing setup for graphene membranes.”
Kidambi’s MIT co-authors are Rohit Karnik, associate professor of mechanical engineering, and Jing Kong, professor of electrical engineering and computer science, along with researchers from Oxford University, the National University of Singapore, and Oak Ridge National Laboratory. Their paper appears today in Advanced Materials.
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