A team of researchers at the Massachusetts Institute of Technology (MIT) has developed a polymer film which produces energy from water vapour.
The new technology could potentially be used in the field of healthcare, in artificial muscle or as power for micro and nano electronic devices.
When placed in contact with a moist surface, the bottom layer of the film absorbs the evaporated water. The film reacts by curling up, but once air hits its bottom layer, the moisture is released. The film then rolls forward and begins to curl up again. This process of constant motion converts the chemical energy of the water gradient into mechanical energy.
“Such films could act as either actuators (a type of motor) or generators,” said professor Robert Langer, who supervised the project. “As an actuator, the material can be surprisingly powerful: we demonstrated that a 25 milligram film can lift a load of glass slides 380 times its own weight and can also transport a load of silver wires 10 times its own weight, working as a potent water-powered mini tractor. Using only water as an energy source, this film could replace the electricity-powered actuators now used to control small robotic limbs.”
Potential commercial applications include large-scale water-vapour power generators or small generators to power wearable electronics. The researchers suggest that if used to generate electricity on a larger scale, the film could harvest energy from the environment, for example, while placed above a lake or river. It could also be attached to clothing, where the evaporation of sweat could fuel devices such as wearable sensors that monitor blood pressure and heart rate.
According to Langer, a six-centimetre by three-centimetre patch of the material can typically generate 5.6nW of electrical power. Although that is not a great deal of power, the generator only needs a small amount of water to function – as little as the sweat on a human hand.
“We are working on making larger generator to produce more power,” he said.
It is clear that the technology could have quite an impact in the medical sector. However, how influential the technology will be is still undetermined.
The National Heart, Lung, and Blood Institute Program of Excellence in Nanotechnology, the National Cancer Institute, and the Armed Forces Institute of Regenerative Medicine acted as funding partners for the research.
“I think it is too soon to determine what the impact will be since the technology is at an early stage of development,” said Dr. Denis B. Buxton of the National Heart, Lung, and Blood Institute. “There are a number of hurdles to be overcome before the technology can be commercialised, including achieving long-term energy generation and achieving sufficient power output to be useful.”
“We are looking forward to seeing what other people propose after reading the paper,” Langer said.