Pulsating Nanotubules Push Out Buckyballs

Scientists have designed nanotubules that pulsate when exposed to changes in temperature. This motion, which mimics the pulsing of biological systems such as car­diac muscle cells, can be used to squeeze out encapsulated buckyball molecules, report Myongsoo Lee of Seoul National University and colleagues (Science, DOI: 10.1126/science.1224741). The work is “stunning and seminal,” Wei Zhang and Takuzo Aida of Japan’s RIKEN Advanced Science Institute say in an accompanying perspective, because the nanotubes could be made to convert thermal energy into anisotropic motion. Lee’s group’s design involves six bent amphiphilic aromatic molecules, which self-assemble to form rings. The bent molecules can slide past each other to expand or contract the ring’s diameter. The rings stack on top of each other to form tubes with a hydrophobic interior. In aqueous solution, the tubes contract and expand from 7 nm to 11 nm in diameter in response to being heated to 60 °C and cooled to room temperature, respectively. The group also made self-assembled tubes containing C₆₀, which was expelled from the tube upon heating.