Scientists at NIST have created 1-cm-long polymer nanotubes that can maintain their shape indefinitely. They could serve as channels for chemicals in nanofluidic reactor devices or as minuscule hypodermic needles for injecting single molecules.
One step in stretching the forming nanotubes
First the researchers made tiny, fluid-filled spherical containers (spin-offs of liposomes) with bi-layer membranes consisting of polymers with one end hydrophilic and the other hydrophobic. To make the membranes stretchy, the investigators added a soap-like fluid that altered their mechanical properties. Then they used optical tweezers (highly focused IR lasers) or micropipettes to pull the membranes into long, double-walled tubes <100 nm in dia. Their next step was to add a chemical to break bonds between atoms in one section of the polymers and induce new bonds to form between the two different sections, forming a rigid cross-linked membrane. Finally, they snipped the nanotubes from the parent cell with an "optical scalpel" (highly focused ultraviolet laser pulse). The nanotubes maintain their shape even after several weeks of storage, and can be removed from the liquid solution and placed on a dry surface or in a different container. The optical tweezers can be used to custom build nanotube network structures. The work was supported in part by the Office of Naval Research, and a paper describing it is available at http://tinyurl.com/f8e2p.