doi:10.1038/nindia.2012.2 Published online 13 January 2012
Researchers have designed a new type of metal-filled nanotube that is propelled like a rocket when irradiated with a controlled electron beam. This rocket-like propulsion could be useful for powering tiny machines and delivering drugs to target cells.
Nanotubes filled with low-melting-point metals are interesting materials because they can be easily manipulated using electron beams and external heat sources to fabricate novel nanosized devices such as nanothermometers and nanorobots. One such nanotube is the indium-filled silica nanotube, which exhibits wonderful electrical properties and high thermal stability.
However, no studies have so far explored the rocket-like propulsion of such nanotubes, which is of interest for powering tiny motors in biomedical applications.
To achieve this goal, the researchers synthesized indium-filled indium oxide nanotubes by heating a mixture of indium oxide and carbon powder in the presence of argon and ethanol. The nanotubes were shaped like rockets, with one open end. The researchers exposed the nanotubes to an electron beam of varying density. The beam selectively melted the indium metal while leaving the nanotubes intact as they have a higher melting point. The presence of the electron beam increased the indium vapour pressure inside the nanotubes along and caused the release of hydrogen gas, owing to the use of ethanol during synthesis. The pressurized gases escaped via an opening similar to the nozzle in a rocket, thus generating a thrust in the opposite direction.
The researchers estimate the thrust generated per unit mass to be an order of magnitude larger than conventional thermal solid rockets used for space applications. "The head of the nanorockets can be tailored to carry loads of specific biological molecules and drugs for targeted delivery at the cellular level," says lead researcher J. P. Singh.
The authors of this work are from: Indian Institute of Technology Delhi, India and Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York, USA.
Kumar, M. et al. Electron beam induced real time rocket-type propulsion effect in indium metal filled indium oxide nanotubes. Mater. Lett. 68, 47-50 (2012) | Article |