Monday, November 22, 2010

Bioluminescent Jellyfish to be used as Solar Cells

Silicon solar cells are so, well, dead. Dollops of green goo made of living cells – from jellyfish to algae - are now being recruited to produce cheaper solar power.

Zackary Chiragwandi at Chalmers University of Technology in Gothenburg, Sweden, and colleagues are developing a photovoltaic device based on green fluorescent protein (GFP) from the jellyfish Aequorea Victoria.

The team deposit two aluminium electrodes with a tiny gap between them onto a silicon dioxide substrate. A droplet of green fluorescent protein is then added on top, whereupon the protein assembles itself into strands between the electrodes.

When exposed to ultraviolet light, the GFP absorbs photons and emits electrons, which travel around a circuit to produce electricity.

Cheap goo

The green goo acts like the dye used in current "dye-sensitised" solar cells, called Grätzel cells.

However, unlike such cells, the GFP does not require the addition of expensive materials, such as titanium dioxide particles. Instead, the GFP can be placed directly on top of the electrode, simplifying the design and reducing overall cost.

The team have also used the proteins to create a biological fuel cell that generates electricity without the need for an external source of light.

Instead, they used light emitted from a mixture of chemicals such as magnesium and the luciferase enzymes found in fireflies (Lampyridae) and sea pansies (Renilla reniformis) to generate electricity from the jellyfish biophotovoltaic device.

Such a fuel cell could be used to power nano-devices embedded in living organisms, says Chiragwandi, for example to diagnose disease.


Jellyfish are not the only sea creatures that can be exploited to generate energy: algae could power floating devices on the ocean wave. Adrian Fisher and Paolo Bombelli at the University of Cambridge and colleagues are developing biophotovoltaic devices based on algae and photosynthetic bacteria.

The team deposit a film of photosynthetic cells on top of a transparent conductive electrode, which faces a carbon cathode seeded with platinum nanoparticles.

When exposed to sunlight the algal cells begin splitting water and producing oxygen, electrons and protons. These would usually be used by the algae to convert carbon dioxide into organic compounds, but instead the device siphons them off to generate electricity, says Fisher. "The algal cells produce electrons very generously," he says.

The team has so far used a proof-of-concept device to power a clock. The sunlight-to-electricity efficiency of the device is only 0.1 per cent at present, compared with between 10 and 15 per cent for existing dye-sensitised solar cells, however. Screening different algae species to find the most productive electron donor might be one way to produce more juice.

Eventually, algal cells could float out at sea, generating electricity from sunlight and seawater. "We might end up with less efficiency than [conventional] photovoltaics, but we think we can win on cost, and we don't require space where people want to live," says Bombelli.

Friday, November 12, 2010

3D Printing

An Opportunity, and a Warning

The next great technological disruption is brewing just out of sight. In small workshops, and faceless office parks, and garages, and basements, revolutionaries are tinkering with machines that can turn digital bits into physical atoms. The machines can download plans for a wrench from the Internet and print out a real, working wrench. Users design their own jewelry, gears, brackets, and toys with a computer program, and use their machines to create real jewelry, gears, brackets, and toys.

These machines, generically known as 3D printers, are not imported from the future or the stuff of science fiction. Home versions, imperfect but real, can be had for around $1,000. Every day they get better, and move closer to the mainstream.

In many ways, today’s 3D printing community resembles the personal computing community of the early 1990s. They are a relatively small, technically proficient group, all intrigued by the potential of a great new technology. They tinker with their machines, share their discoveries and creations, and are more focused on what is possible than on what happens after they achieve it. They also benefit from following the personal computer revolution: the connective power of the Internet lets them share, innovate, and communicate much faster than the Homebrew Computer Club could have ever imagined.

The personal computer revolution also casts light on some potential pitfalls that may be in store for the growth of 3D printing. When entrenched interests began to understand just how disruptive personal computing could be (especially massively networked personal computing) they organized in Washington, D.C. to protect their incumbent power. Rallying under the banner of combating piracy and theft, these interests pushed through laws like the Digital Millennium Copyright Act (DMCA) that made it harder to use computers in new and innovative ways. In response, the general public learned once-obscure terms like “fair use” and worked hard to defend their ability to discuss, create, and innovate. Unfortunately, this great public awakening came after Congress had already passed its restrictive laws.

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Tuesday, November 2, 2010

World's Largest Living Thing

The largest living organism ever found has been discovered in an ancient American forest.

The Armillaria ostoyae, popularly known as the honey mushroom, started from a single spore too small to see without a microscope. It has been spreading its black shoestring filaments, called rhizomorphs, through the forest for an estimated 2,400 years, killing trees as it grows. It now covers 2,200 acres (880 hectares) of the Malheur National Forest, in eastern Oregon.

The outline of the giant fungus stretches 3.5 miles (5.6 kilometres) across, and it extends an average of three feet (one metre) into the ground. It covers an area as big as 1,665 football fields.

The discovery came after Catherine Parks, a scientist at the Pacific Northwest Research Station in La Grande, Oregon, in 1998 heard about a big tree die-off from root rot in the forest east of Prairie City.

Using aerial photos, Ms Parks staked out an area of dying trees and collected root samples from 112. She identified the fungus through DNA testing. Then, by comparing cultures of the fungus grown from the 112 samples, she determined that 61 were from the same organism, meaning a single fungus had grown bigger than anything anyone had ever described before.

On the surface, the only evidence of the fungus are clumps of golden mushrooms that pop up in the autumn with the rain. "They are edible, but they don't taste the best," said Tina Dreisbach, a botanist and mycologist with the US Forest Service in Corvallis, Oregon. "I would put lots of butter and garlic on them."

Digging into the roots of an affected tree, something that looks like white latex paint can be seen. These are mats of mycelium, which draw water and carbohydrates from the tree to feed the fungus and interfere with the tree's absorption of water and nutrients. The long rhizomorphs that stretch into the soil invade tree roots through a combination of pressure and enzyme action.

In 1992, another Armillaria ostoyae was found in Washington state covering 1,500 acres, near Mount Adams, making it the largest known organism at the time.

"We just decided to go out looking for one bigger than the last claim," said Gregory Filip, associate professor of integrated forest protection at Oregon State University, and an expert in Armillaria. "There hasn't been anything measured with any scientific technique that has shown any plant or animal to be larger than this."

He said scientists want to learn to control Armillaria because it kills trees, but they also realise it has served a purpose in nature for millions of years.

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