Nanotubes have biotech future

Scientists at the

(NIST) have created longer, stronger nanotubes with potential to be used in a variety of biotechnology applications.

The polymer nanotubes are about one centimetre long and very stable, being able to maintain their shape indefinitely. The NIST research says that the nanotubes may have biotechnology applications as channels for tiny volumes of chemicals in nanofluidic reactor devices, or as microscopic hypodermic needles for injecting molecules one at a time.

Carbon is usually the material of choice for making strong nanotubes, but polymers are better in biochemical applications. However, the polymer nanotubes built to date are very fragile. The NIST team developed processes for keeping polymer nanotubes stable.

The researchers made tiny, fluid-filled spherical containers with bi-layer membranes consisting of polymers with one hydrophilic end and one hydrophobic end, using liposome technology. The researchers made the membranes pliable by adding a soap-like fluid to change the polymer membranes' mechanical properties. Then they used highly focused infrared lasers, dubbed "optical tweezers" to pull on the elastic membranes to form long, double-walled tubes that are less than 100 nanometres in diameter.

A chemical was added to break bonds between atoms and reform bonds between sections of the polymer, forming a rigid "cross-linked" membrane. The nanotubes were then snipped free from the parent cell with a highly focused ultraviolet laser pulse, known as an "optical scalpel".

The nanotubes maintain their shape even after several weeks of storage, and can be removed from the liquid solution to other locations, even a dry surface. The optical tweezers can be used to custom build nanotube network structures.