The team from National Chung Hsing University, Taiwan, and Carnegie Mellon University (CMU), US, is applying the technique to develop tissue scaffolds. To be successful, the researchers need full control over the substrate's 3D architecture and that's where the so-called dielectrophoretic approach comes in.

"We use an electric field to drive the CNTs vertically into the polymer material," Chao-Min Cheng of CMU’s cellular biomechanics laboratory told "Using our method, we can ensure that the CNTs are distributed uniformly on the surface."

By controlling the nanotopography of the tissue scaffold, the group aims to improve key performance markers such as cell attachment and cell spreading.

To make the composite material, Cheng and his colleagues begin by spin-coating a 10 µm-thick polymer (SU-8) layer on to a clean silicon substrate. Next, a drop of MWCNTs dispersed in dimethyl formamide is placed on to the polymer surface and an AC voltage applied across the sample, which embeds the nanotubes in the SU-8.

Tapping mode AFM images of the final surface reveal a topography that is rich in protrusions and cavities.

Pleased with the result, the researchers put their material to the test by culturing 3T3 fibroblast cells on the surface. Optical phase contrast images taken 36 and 84 hours later show the attachment, spreading and proliferation of cells.

The researchers presented their work in Electrophoresis.