The "Flying Carpet"

The sheet is lifted by the air packets, and propelled forwards

A miniature magic carpet made of plastic has taken flight in a laboratory at Princeton University.

The 10cm (4in) sheet of smart transparency is driven by "ripple power"; waves of electrical current driving thin pockets of air from front to rear underneath. 

The prototype, described in Applied Physics Letters, moves at speeds of about a centimeter per second.

Improvements to the design could raise that to as much as a meter per second.

The device's creator, graduate student Noah Jafferis, says he was inspired by a mathematical paper he read shortly after starting his PhD studies at Princeton.

He abandoned what would have been a fashionable project printing electronic circuits with nano-inks for one that seemed to have more in common with 1001 Nights than 21st-Century engineering.

Prof James Sturm, who leads Mr Jafferis' research group, conceded that at times the project seemed foolhardy.

"What was difficult was controlling the precise behaviour of the sheet as it deformed at high frequencies," he told the BBC. 

"Without the ability to predict the exact way it would flex, we couldn't feed in the right electrical currents to get the propulsion to work properly."

What followed was a two year digression attaching sensors to every part of the material so as to fine-tune its performance through a series of complex feedbacks.

But once that was mastered, the waveform of the undulating matched that prescribed by the theory, and the wafting motions gave life to the tiny carpet.

In the paper describing the design, Mr Jafferis and his co-authors are careful to keep the word "flying" in inverted commas, because the resulting machine has more in common with a hovercraft than an aeroplane.

"It has to keep close to the ground,  because the air is then trapped between the sheet and the ground. As the waves move along the sheet it basically pumps the air out the back." That is the source of the thrust.

Ray hope

  

Harvard University's Lakshminarayanan Mahadevan, who wrote the 2007 paper in Physical Review Letters that inspired the whole project, expressed a mixture of surprise and delight at the Princeton team's success.

                                   The propulsion is not completely unlike that of skates and rays

"Noah has gone beyond our simple theory and actually built a device that works," he told the BBC "And what's more, it behaves, at least qualitatively, as we had predicted."

Mr Jafferis points out that the prototype is limited because tiny conducting threads anchor it to heavy batteries, so it's free to move only a few centimetres. But he is already working on a solar-powered upgrade that could freely fly over large distances.

The advantage of this kind of propulsion, he argues, is that unlike jets, propellers and hovercraft, there are no moving components like cogs and gears that rub against each other.

"The ideal use would be some kind of dusty, grimy environment where moving parts would get gummed up and stop," he explained.

That said, he laughingly admits that with the existing materials, a flying carpet powerful enough to carry a person would need a wingspan of 50 metres - not the best vehicle to take on the streets just yet.

On the other hand, preliminary calculations suggest that there is enough atmosphere on the planet Mars to send floating rovers scudding over its dusty surface.

Meanwhile, Prof Mahadevan looks forward to sophisticated improvements in the near future, suggesting the approach could progress to "mimicking the beautiful two-dimensional undulations of the skate or manta ray". 

by "environment clean generations"

Synthetic Trees Better Than Real Ones?

Baobab Trees These baobab trees, native to Africa and Australia, are an important part of the Madagascar deciduous forest. Some baobabs are believed to be thousands of years old, but since the wood does not create annual growth rings, it is difficult to track their growth. The trees are a hardy breed though, with some Madagascar species growing directly out of limestone rock.

Trees are great absorbers of carbon dioxide from the atmosphere, and inhibitors of climate change -- that's why treehuggers hug them so much. But leave it to humanity to engineer a better tree. A synthetic tree, currently being tested as a prototype, ensnares carbon about 1,000 times faster than a real tree.

The "tree" uses plastic leaves that capture the carbon dioxide in a chamber. The carbon dioxide is then compressed into liquid form. The tree captures the carbon without the need for direct sunlight, which means that, unlike traditional trees, the synthetic trees can be stored in enclosed places such as barns, used anywhere, and transported from one site to another regardless of conditions. 

Lackner says the captured CO₂ could be used to create fuel for jet engines and cars, the two most common carbon emitters. In other cases, the CO₂ could be used to enhance current production of vegetable produce.

Klaus Lackner, a professor at Columbia University who is developing the tree, met with U.S. Energy Secretary Steven Chu last month to talk about the concept. In an interview with CNN, Lackner said the synthetic tree is "several hundred times better at collecting CO₂" than windmill generators. 

Lackner says that for every 1,000 kilograms of carbon dioxide collected, the tree emits just 200 kilograms. This ratio is more than enough to warrant the relatively high cost of building the trees (about the same as a new automobile) or retrofitting coal plants.

Each synthetic tree could collect about 90,000 tons of carbon per year.

by "environment clean generations"