Nanotechnology bulks up artificial muscles
Date: 18.4.2006
Researchers at the University of Texas at Dallas, US, and Pusan National University in Korea have made two types of artificial muscle based on nanotechnology. The muscles convert chemical energy to mechanical energy and could have applications in robotics.
The first type of device employed a carbon nanotube cantilever. Dubbed a cantilever-based nanotube fuel-cell muscle, the system converted chemical energy (in the form of hydrogen fuel) to electrical energy, which it could then use for movement, other needs or storage.
The cantilever consisted of a strip of nanotube sheet covered with platinum-coated carbon and the ionic polymer Nafion. As well as functioning as the muscle actuator, this structure formed the cathode of the fuel cell and was immersed in sulphuric acid electrolyte. Also in contact with the electrolyte was a second electrode formed from a platinum-carbon-Nafion layer on a Nafion-117 membrane. This membrane separated the hydrogen fuel from the electrolyte.
Actuation of the nanotube sheet resulted from the injection of holes that took place when oxygen was reduced at the nanotube electrode. Hole injection produced a dimensional change in the sheet because of a combination of quantum mechanical and electrostatic effects. The 3 cm-long nanotube cantilever deflected by around 2 mm in roughly 5 s. Shorting the electrodes returned the cantilever to its original position in around 1 s.
The team's continuously shorted fuel-cell muscle, on the other hand, incorporated a shape-memory wire coated with nanoparticles of platinum catalyst. This type of muscle converted the chemical energy of the fuel into thermal energy, which caused actuation.
Made from nickel titanium alloy, the shape-memory wire acted as a single electrode, functioning as a shorted electrode pair. Adding oxygen or air to fuel in the form of hydrogen, methanol vapour or formic acid vapour caused the wire to heat above its austenitic phase transition temperature and contract.
"Source":[ http://nanotechweb.org/articles/news/5/3/18?alert=1].
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