An artificially structured material — or metamaterial — made of specially patterned polymers may enable more-efficient, energy-saving membrane separations, believe researchers at the Georgia Institute of Technology (Georgia Tech), Atlanta. They have designed what they claim is the first metamaterial that can sort chemical and biomolecular species.
“With this metamaterial, we can control the direction the atoms can go using the trick of anisotropy,” explains Martin Maldovan, an assistant professor in the School of Chemical and Biomolecular Engineering. “This would be in addition to separation based on solubility and diffusivity. We have added an important parameter to the toolbox of chemical engineers: where to send the atoms.”
[javascriptSnippet ]
The researchers have performed computational studies on a metamaterial consisting of four different types of polymers, two with high diffusivity and two with low diffusivity. They used mathematical algorithms to determine the size and patterning of blocks made from each material. The metamaterial achieves separation by cloaking one compound while concentrating the other.
“By designing the diffusivity of the metamaterials, we can make the atoms of one compound go one way, and the atoms of another compound go a different way. We are manipulating the physical properties to control the directions that atoms take through the metamaterial shell,” notes Maldovan.
The result is an anisotropic metamaterial — i.e., one whose structure favors flow in certain directions — that can direct a specific chemical around the shell or concentrate it within the shell (Figure 1).
