Optical devices get fishy

Scientists in the US have used the DNA from fish waste to make optical components. The team, led by James Grote of the US Air Force Research Laboratory, says that the material could be used to make optical waveguides, modulators and light-emitting diodes. They also claim that fish DNA, which is abundant and environmentally friendly, could outperform other polymer-based devices.

DNA has unique electronic and optical properties. It has low optical loss over a broad range of wavelengths and its electrical resistivity is three to five orders of magnitude lower than other polymers. Moreover, the resistivity of the DNA can be tweaked by changing the molecule's molecular weight.

According to Grote's team, which includes researchers from the universities of Dayton and Cincinatti, the material could be used to make a waveguide device that could have lower optical losses than other polymers. "There is also promise for both passive and active all DNA devices such as electro-optic modulators," adds Grote.

The team obtained the DNA by treating a mix of salmon milt and roe sacs with enzymes to remove unwanted proteins. They then purified the material by dissolving it in an organic solvent and filtering it through a membrane. Finally, they used the technique of 'spin deposition' to create thin DNA films on a substrate that are stable up to 200 degrees celsius. By cross-linking DNA - joining neighbouring molecules through chemical bonds - the team was able to toughen the material and create multi-layer structures.