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New material harvests energy from water vapor

Fri, 05 Apr 2013 11:31:04 GMT

MIT engineers have created a new polymer film that can generate electricity by drawing on a ubiquitous source: water vapor.

The new material changes its shape after absorbing tiny amounts of evaporated water, allowing it to repeatedly curl up and down. Harnessing this continuous motion could drive robotic limbs or generate enough electricity to power micro- and nanoelectronic devices, such as environmental sensors.

“With a sensor powered by a battery, you have to replace it periodically. If you have this device, you can harvest energy from the environment so you don't have to replace it very often,” says Mingming Ma, a postdoc at MIT’s David H. Koch Institute for Integrative Cancer Research and lead author of a paper describing the new material in the Jan. 11 issue of Science.

“We are very excited about this new material, and we expect as we achieve higher efficiency in converting mechanical energy into electricity, this material will find even broader applications,” says Robert Langer, the David H. Koch Institute Professor at MIT and senior author of the paper. Those potential applications include large-scale, water-vapor-powered generators, or smaller generators to power wearable electronics.

Other authors of the Science paper are Koch Institute postdoc Liang Guo and Daniel Anderson, the Samuel A. Goldblith Associate Professor of Chemical Engineering and a member of the Koch Institute and MIT’s Institute for Medical Engineering and Science.

Harvesting energy

The new film is made from an interlocking network of two different polymers. One of the polymers, polypyrrole, forms a hard but flexible matrix that provides structural support. The other polymer, polyol-borate, is a soft gel that swells when it absorbs water.

Previous efforts to make water-responsive films have used only polypyrrole, which shows a much weaker response on its own. “By incorporating the two different kinds of polymers, you can generate a much bigger displacement, as well as a stronger force,” Guo says.

The film harvests energy found in the water gradient between dry and water-rich environments. When the 20-micrometer-thick film lies on a surface that contains even a small amount of moisture, the bottom layer absorbs evaporated water, forcing the film to curl away from the surface. Once the bottom of the film is exposed to air, it quickly releases the moisture, somersaults forward, and starts to curl up again. As this cycle is repeated, the continuous 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. As an actuator, the material can be surprisingly powerful: The researchers demonstrated that a 25-milligram film can lift a load of glass slides 380 times its own weight, or transport a load of silver wires 10 times its own weight, by 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.

“It doesn't need a lot of water,” Ma says. “A very small amount of moisture would be enough.”

A key advantage of the new film is that it doesn’t require manipulation of environmental conditions, as do actuators that respond to changes in temperature or acidity, says Ryan Hayward, an associate professor of polymer science and engineering at the University of Massachusetts at Amherst.

“What’s really impressive about this work is that they were able to figure out a scheme where a gradient in humidity would cause the polymer to cyclically roll up, flip over and roll in the other direction, and were able to harness that energy to do work,” says Hayward, who was not part of the research team.

Generating electricity

The mechanical energy generated by the material can also be converted into electricity by coupling the polymer film with a piezoelectric material, which converts mechanical stress to an electric charge. This system can generate an average power of 5.6 nanowatts, which can be stored in capacitors to power ultra-low-power microelectronic devices, such as temperature and humidity sensors.

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. Or, it could be attached to clothing, where the mere evaporation of sweat could fuel devices such as physiological monitoring sensors. “You could be running or exercising and generating power,” Guo says.

On a smaller scale, the film could power microelectricalmechanical systems (MEMS), including environmental sensors, or even smaller devices, such as nanoelectronics. The researchers are now working to improve the efficiency of the conversion of mechanical energy to electrical energy, which could allow smaller films to power larger devices.

The research was funded by the National Heart, Lung, and Blood Institute Program of Excellence in Nanotechnology, the National Cancer Institute, and the Armed Forces Institute of Regenerative Medicine.

Environmental pollution control needs public attention

Mon, 25 Mar 2013 10:58:01 GMT

(VEN) - The Law on Environmental Protection (LEP) issued in 2005 has 15 chapters and 136 articles, increased by 8 chapters, 79 articles compared to LEP enacted in 1993. However, to meet the current situation, the LEP 2005 should be amended, with social responsibility and public environmental pollution control receiving greater emphasis.

No regulations on air pollution control

According to Prof. Dr. Pham Ngoc Dang, President of the Vietnam Clean Air Network (VCAP), LEP 2005 did not have any regulations on air and land environmental protection. These shortcomings in the LEP 2005 contributed to an seriously increased risk of air pollution.

According to research results of the "Assessing the overall health and economic damage caused by air pollution" project in 2010, co-launched within the framework of the Program 23 on improving air quality in urban areas by the Department of Health and Ministry of Transport, the financial damage caused by air pollution-related diseases per day per person living Hanoi was VND1,538 and VND739 per day per person living Ho Chi Minh City. By a rough reckoning, Hanoi citizens must incur around US$66.83 million damage and Ho Chi Minh City dwellers US$70.96 million.

According to Pham Ngoc Dang, to effectively control air pollution, the amended LEP should include to air environmental protection regulations regarding urban areas, handicraft villages, industrial zones, and rural areas; traffic noise, industrial noise and social noise; and also transboundary air pollution issues.

Water pollution control needs due attention from the public.

According to Prof. Dr. Tran Hieu Nhue from the Vietnam Association for Conservation of Nature and Environment, currently there are about 2,500 craft villages across the country, but very few of them have adopted effective wastewater treatment solutions. Moreover, only 143 of 235 working industrial parks nationwide have built centralized wastewater treatment systems; and especially, only 18 of 1,000 industrial clusters across the country have owned centralized wastewater treatment systems.

Although the articles 35, 36, 37, 38, 44, and 82 in Chapter VIII clearly stipulate the environmental protection responsibilities of organizations, individuals, industrial parks, industrial clusters, and craft villages, there has been no strict implementation in accordance over the past seven years. Therefore, the amended LEP should include regulations on public inspection and control of environmental protection conducted by investors in infrastructure investment projects made in industrial parks and industrial clusters.

And the important role of the public

The LEP 2005 has provisions to create a legal basis for public participation in environmental protection. However, these regulations have proved limited and need amendment. According to Dr. Nguyen Van Phuong from Hanoi Law University, the Articles 103,104 and 105 in LEP 2005 regulate the publicity of environmental data and protection measures by organizations and individuals involved in production and trade of goods.

However, the public can passively receive the environmental data from producers and traders. So, what should be considered in the amended LEP is whether the public can actively require these producers and traders to provide necessary environmental information and what scope of information the public is able to ask for.

In addition, the amended LEP should include more regulations on ensuring public participation in environmental protection, and measures to improve public awareness of environmental protection and mechanisms to encourage the public participation in environmental protection activities.

The policy on public participation in environmental protection has proved sound in many countries worldwide and will play an important role in the national environmental protection program. However, it is necessary to have the bylaws to clarify mechanisms to ensure implementation of the public's rights to know, discuss, do, check, complaint and denunciate environmental protection activities./.

We know that real trees soak up carbon from the atmosphere — but fake trees?

Mon, 24 Dec 2012 06:50:16 GMT

A cheap plastic that removes carbon dioxide (CO2) from the atmosphere? “Yes,” says a team of chemists at the University of Southern California’s (USC) Loker Hydrocarbon Research Institute, led by Nobel Prize winner George Olah. Science Now reports on their work with an inexpensive polymer called polyethylenimine or PEI.

But how to maximize its absorption capabilities? Olah’s team dissolved the polymer in a solvent and spread it out, peanut-butter-style, on fumed silica — you know, like the stuff in those desiccant packets in your electronics packaging (“Do not eat,” by the way). It’s also used as a stabilizer for lipstick and other make-up.

And you thought plastic palm trees had no redeeming value..

Here are the geeky details from Science Now:

When the researchers tested the new material’s CO₂-grabbing abilities, they found that in humid air—the kind present in most ambient conditions—each gram of the material sopped up an average of 1.72 nanomoles of CO₂. That’s well above the 1.44 nanomoles per gram absorbed by a recent rival made from aminosilica and among the highest levels of CO₂ absorption from air ever tested, the team reported last month in the Journal of the American Chemical Society. Once saturated with CO₂, the PEI-silica combo is easy to regenerate. The CO₂floats away after the polymer is heated to 85°C. Other commonly used solid CO₂ absorbers must be heated to over 800°C to drive off the CO₂.

Team member Surya Prakash says the polymer could also be used to make vast farms of artificial “trees” that could suck CO2 out of the atmosphere, much like real ones do. Prakash and Olah have been trying to stand the carbon paradigm on its ear for the past several years, exploring it as a positive rather than a negative for the planet. “People tend to think of CO₂ as a problem rather than a resource,” he explained. “We want to take CO₂, and instead of burying it underground, use it as a raw material, and convert it with alternative energy sources back to fuels and feedstocks.”

(Excerpted from KQED-Climate Watch, January 11, 2012) By Kimberly Ayers

About the author

Kimberly Ayers has lived in California for more than 20 years, both north and south. Growing up in the Middle East as an "oil brat," she has been blessed with lots of travel. Her storytelling has appeared most recently on the National Geographic Channel, including reporting from Belize and Egypt. For the past four years, she has produced the PBS stations' broadcast of the National Geographic Bee: the questions are really hard, and the kids are crazy-smart. At forty-something, she walked the Catalina Marathon, and most mornings you will find her walking somewhere on the SoCal coast.