Nanotubes as highly selective membrane pores
Researchers in the US have developed a membrane containing pores made of carbon nanotubes. Water and gas transport through the sub-two-nanometer passages far exceeded theoretical predictions. The extremely smooth inner surface of the tubes is probably responsible for this.
The researchers led by Olgica Bakajin from the Lawrence Livermore National Laboratory first grew a forest of vertical nanotubes on a silicon chip and then filled the gaps with a silicon nitride matrix. They then etched away the substrate in a targeted manner in some places, thereby opening up the nanopore passages.
When the scientists measured the flow of gas or water, they came up with speeds that were one hundred to ten thousand times higher than the theoretically expected values. The permeability of the new membrane is thus significantly higher than that of conventional polycarbonate materials, although the pore diameters are several orders of magnitude smaller. Bakajin and her team speculate that their new membrane could prove itself in desalination plants or drinking water treatment, for example.
