IEEE Future Directions
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Graphene has been around for some years now and its properties are well understood. Most of the work is focussing on the creation of industrial processes to deliver usable sheets of graphene at an affordable cost in volumes.
Graphene per sé is a one atom thick layer of carbon atoms forming a chicken grid (hexagonal patterns). By introducing alien atoms (not carbon) one can alter the shape of the grid and the characteristics of the layer, like its conductivity (it is possible, as an example, to create a Schottky junction -a transistor).
Researchers at MIT have managed to create layers made of graphene with specific gaps in the grid. This makes possible to use them as membrane for dialysis. Dialysis is a filtration process, the word is mostly known in relation to supporting procedure for malfunctioning kidneys but it applies more generally to any kind of filtration.
By modifying the gaps in the layer it is possible to create membranes that filter any kind of molecules, from potassium chloride -0.66nm- to lysozyme -4nm- (a protein in the egg white). Even more interesting is the dialysis efficiency: a graphene based membrane can filter 10x the speed of industrial membranes used today. This is because the membrane consists of a single atom layer, whilst today’s membranes are (relatively speaking) “thick”.
The gap modification is achieved by exposing, in a controlled process, the graphene layer to oxygen plasma. This leads to oxygen “eating” a carbon atom removing it from the grid (flying away as CO). By regulating the flow of the plasma researchers can create smaller or larger gaps in the grid thus resulting in a membrane specific for filtering a given molecule size.
Currently the process produces membrane having a 1 square cm size. Researchers are working to increase this size to increase the filtration output.
