Physicists pull off the gecko's feat

For years scientists have tried — and failed — to engineer materials that would enable robots to mimic the gecko’s ability to scale walls, windows and seemingly any other surface. Now, a team from the US has developed a nanotube material that is not just a match for gecko feet but 10 times more adhesive.

Look close enough at a gecko foot and you will see an ordered, forest-like structure — roughly half a million fine hairs that each sprout into hundreds of even thinner, spatula-shaped tips. When these tips come into close contact with a surface they induce strong van der Waals forces that keep the foot anchored — that is, until the gecko decides to peel it off.

In the past scientists have attempted to copy this hair structure by fabricating arrays of polymer pillars, but these can sustain little more than a third of the gecko’s adhesive force. Although nanotubes have proved better, it is difficult to replicate the delicate tip structure of gecko hairs that would enable the nanotubes to reach their theoretical limit.

Stuck on you

The US team, led by Zhong Lin Wang of Georgia Institute of Technology, has made a structure that looks at least similar to gecko feet through chemical vapour deposition of an ethyne–hydrogen–argon gas over a silicon substrate. By introducing an iron catalyst on the substrate and controlling the temperature and duration of deposition, the team end up with an array of vertical nanotubes with spiralled, fuzzy tips.

In tests on glass, sandpaper and plastic, Wang and colleagues found that their nanotube material exhibited adhesive forces of about 100 Ncm^–2, almost an order of magnitude greater than a gecko foot (Science 322 238). That is strong enough for a 4 × 4 mm pad of the material to suspend a 1.5 kg hardback textbook. “In future work modifying the surface of the nanotubes with polymers, proteins, etc, we should be able to make the adhesive nanotubes stick to a wide variety of surfaces,” Liming Dai, one of the team members, told physicsworld.com.

Mark Geoghegan, a physicist from the University of Sheffield, UK, thinks an advantage of the US team’s fabrication technique is that it does not use expensive lithography — although it is still not cheap. “A pack of 20 super-strong carbon-nanotube post-it notes would probably cost well over $1000 per note,” he jokes.

Pulls off normally

A more fundamental advantage of Wang and colleagues’ material is that it is not stoutly adhesive in all directions. If the material is stuck to a wall it will resist a strong downwards tug, but if it is pulled directly away (that is, along the normal) the nanotubes can peel off one by one. It is this property that allows geckos to hang from walls while being able to prize off their feet to scurry around.

Dai says he and the team are now planning to optimize the structure and scale it up so that they can make “spiderman” gloves.

Physicists pull off the gecko's feat

For years scientists have tried — and failed — to engineer materials that would enable robots to mimic the gecko’s ability to scale walls, windows and seemingly any other surface. Now, a team from the US has developed a nanotube material that is not just a match for gecko feet but 10 times more adhesive.

Look close enough at a gecko foot and you will see an ordered, forest-like structure — roughly half a million fine hairs that each sprout into hundreds of even thinner, spatula-shaped tips. When these tips come into close contact with a surface they induce strong van der Waals forces that keep the foot anchored — that is, until the gecko decides to peel it off.

In the past scientists have attempted to copy this hair structure by fabricating arrays of polymer pillars, but these can sustain little more than a third of the gecko’s adhesive force. Although nanotubes have proved better, it is difficult to replicate the delicate tip structure of gecko hairs that would enable the nanotubes to reach their theoretical limit.

Stuck on you

The US team, led by Zhong Lin Wang of Georgia Institute of Technology, has made a structure that looks at least similar to gecko feet through chemical vapour deposition of an ethyne–hydrogen–argon gas over a silicon substrate. By introducing an iron catalyst on the substrate and controlling the temperature and duration of deposition, the team end up with an array of vertical nanotubes with spiralled, fuzzy tips.

In tests on glass, sandpaper and plastic, Wang and colleagues found that their nanotube material exhibited adhesive forces of about 100 Ncm^–2, almost an order of magnitude greater than a gecko foot (Science 322 238). That is strong enough for a 4 × 4 mm pad of the material to suspend a 1.5 kg hardback textbook. “In future work modifying the surface of the nanotubes with polymers, proteins, etc, we should be able to make the adhesive nanotubes stick to a wide variety of surfaces,” Liming Dai, one of the team members, told physicsworld.com.

Mark Geoghegan, a physicist from the University of Sheffield, UK, thinks an advantage of the US team’s fabrication technique is that it does not use expensive lithography — although it is still not cheap. “A pack of 20 super-strong carbon-nanotube post-it notes would probably cost well over $1000 per note,” he jokes.

Pulls off normally

A more fundamental advantage of Wang and colleagues’ material is that it is not stoutly adhesive in all directions. If the material is stuck to a wall it will resist a strong downwards tug, but if it is pulled directly away (that is, along the normal) the nanotubes can peel off one by one. It is this property that allows geckos to hang from walls while being able to prize off their feet to scurry around.

Dai says he and the team are now planning to optimize the structure and scale it up so that they can make “spiderman” gloves.

Zuumer Electric Scooter: Hands-On, First Drive

Zuumer inventor Tom Boyd with his baby.

It’s official - I’m buying one. After just a single ride on Zuumcraft’s new Zuumer Electric Scooter, I’ve just put my $250 down payment for my very own unit. Why? Because the Zuumer is the single most innovative, most useful, and most fun VLEV (Very Light Electric Vehicle) that I’ve ever ridden, and I’ve tried a few. And I don’t impress easily.

The Zuumer Electric scooter is a new kind of VLEV invented by Tom Boyd of Zuumcraft, Inc., of San Diego, CA - it’s a three-wheel electric stand-up scooter that uses an innovative new suspension system on the rear wheels of the unit. This suspension system allows both rear wheels to independently lean into the angle of a turn similarly to how a motorcycle would do. The combination of the two rear wheels and the independent suspension system allows you to ride this scooter very similarly to how you might a skateboard or snowboard. In fact, the closest feeling that I can describe to how riding a Zuumer feels is that it is like snowboarding a road. Except, you can snowboard up hill.

Hands-on With the Zuumer

I live in San Diego and had the opportunity to meet Tom Boyd, the inventor of the Zuumer, and ride one of his scooters. Tom calls himself an evangelist of electric vehicles and the Zuumer, and it shows; his passion for his product and the EV industry was evident as soon as he got out of his truck at the bike trailhead where we met. And true to the Zuumer’s appeal, I barely had time to shake his hand before someone walked up to check one out and proceeded to ask a ton of interested questions.

Tom spent some time showing me some of the unique and innovative features of the Zuumer. The Zuumer features:

The front wheel of the Zuumer - the 1000 watt motor is integrated into the wheel hub.		The rear wheel assembly. Notice how the rear wheels stay perpendicular to the plane of the floorboard - this is what makes the Zuumer so stable and responsive.

That awesome independent rear suspension: this is the heart of this device, and once you get on and you ride it, you’ll understand why it’s such a big deal. You can carve and cut very sharp and quick corners on this vehicle, and it remains stable at top speed - unlike many other stand-up scooters I’ve tried. Once you learn how to shift your body weight and turn by changing your center of gravity, you’re not driving anymore - you’re surfing, and it is exhilarating. For those that have always wanted to feel what it’s like to surf, or snowboard, or skateboard, get on a Zuumer - you’ll get to a similar feeling with a much quicker learning curve.

A 1000 watt brushless front hub motor: This thing’s got power - 20mph top speeds are for real, not just a claim. And the unit didn’t slow down all that much going uphill. The fact that it’s integrated into the front hub makes this motor more efficient, less prone to wear, quieter, and easier to maintain than a motor with a chain or belt drive.

Another shot of the independent rear suspension system.		The modular battery pack under the scooter’s floorboard. Tom is sliding one out to illustrate how they are removed from the unit.

Two Modular Lithium Polymer batteries: Each battery is modular, and features a unique digital display that tells you how much charge and riding time is left on the battery. You can take the batteries out of the unit, and recharge them at home - there’s no need to wheel the whole scooter into your house to recharge. Together both batteries provide you with 20 miles of range. This is nothing short of amazing for a stand-up scooter, and is by far the longest claimed range I’ve ever seen for a scooter of this size.

An intelligent motor and battery controller: If the battery charge gets low, a ‘limp home’ mode kicks in that will slow down the motor to ensure you have enough charge to get home without completely discharging the batteries. This is useful when you get caught off guard with a low battery charge. You’ll get home slower, but you’ll get home.

A key less alarm system: This feature is the pinnacle of cool and useful. Basically, you get a key fob just like your car alarm. Press a button, and the unit turns itself on and is ready for action. Press another button, and the power is killed, and the alarm turns on. A mercury switch in the vehicle will activate a loud alarm if anyone tries to walk off with your scooter (the scooter will not operate with the alarm on). Another button activates a ‘panic’ mode, setting off the alarm. I have to say, this feature alone adds tremendous value to this product, as you can confidently step away from your prized scooter without worrying about it getting stealthily wheeled off while you’re getting your coffee. A definite real-life concern with my current unit, and a concern for anyone living in an urban environment.

The left handlebar. Notice the buttons for lights and the horn.		The right handlebar. Notice the electronic key dangling from the handlebar, and above it the cruise control button.

Cruise control: Yeah, you read that right. Cruise control. Crank up the throttle to the desired speed, press a button, and the scooter will remain at that speed until you hit the brakes. Now you’re riding! Now grab on to the middle of the handlebar with your leading hand, turn sideways, and you’ve got yourself a motorized snowboard, able to carve uphill or downhill. What a feeling - I know, I tried it. Seriously however, this feature will appeal to anyone who has ever ridden a stand-up scooter and knows what a pain it is to maintain a desired speed. The cruise control leaves you free to enjoy what the Zuumer is all about - that awesome feeling of surfing the concrete, at 20 mph.

Headlight, brake/taillight, and horn: You can ride the Zuumer at night if you need to, as the Zuumer includes a very light LED headlight and tailight system. A brake light also illuminates when you activate the brakes. A loud horn is also provided on the unit for when you need to get those slowpokes out of your way.

Three disk brakes: The Zuumer can safely stop from 20mph in less than 15 feet, and can do it without you flying off the unit. That’s impressive.

Adjustable handlebars: Short or tall, the Zuumer takes them all. The handlebars are adjustable, so you can set them to whatever height is comfortable for you.

Solid construction throughout: The Zuumer I rode was a pre-production model and made from high-quality machined aluminum and steel - it felt rock-solid to drive and was a thing of beauty to behold. The production models will be just as well-constructed, Tom said.

The Zuumer in all its glory.

How much does it cost for all this goodness? The retail price is currently set at $2,195, and Zuumcraft is taking deposits now for its first batch of Zuumers, due out in January 2009. I have to tell you, it’s great to already know what I’m getting for Christmas!

Tom calls the Zuumer “Cool, Green, Fun” and I have to agree with him on that point. All in all, I got to spend about an hour riding on the Zuumer with Tom, and it was exhilarating. I was able to ride the unit standing forward, like on a traditional stand-up. I was also able to ride it sideways, like a skateboard or snowboard. The unit was responsive to my every shift and turn, and I was quickly carving lazy S’es on the road. When we came to turns, I was able to lean into them and take them steeply at speeds which would have had me flying off of my regular stand-up. All in all, it was amazingly fun. At the end of my ride, I found myself stalling for more time, just to get a few more minutes with the device. What sucks now is that I have to wait for three months to get my hands on my own unit.

Tom and Zuumcraft are planning to sell the Zuumer directly online through their website, http://www.zuumcraft.com and have identified several target markets to sell the device to. I think that anyone who is interested in getting an alternative transportation device of any kind should take a good look at the Zuumer - in my mind, the target market is anyone who is interested in a fun, fast, and useful personal electric transportation device.

5 Dirty Aspects of “Clean” Coal

Clean coal has been getting a lot of attention lately. Both Mr. McCain and Mr. Obama consider it to be an important piece in their energy plans. Even the recent $900 billion bailout package included $1.5 billion for clean coal. Because coal is so plentiful and relatively cheap in the US, the notion of clean coal is particularly appealing. Unfortunately, clean coal is a myth.

Here’s why clean coal is so dirty:

1. Clean Coal Requires More Coal

30% more energy is required to pump carbon underground for carbon capture and sequestration (CCS). The captured carbon dioxide has to be compressed to 100 times the atmospheric pressure, transferred to an underground storage reservoir and then pumped in the ground. All of this requires large amounts of energy, thus the coal plant must burn an additional 30% more coal to generate the same amount of usable electricity.

2. High Expenses Make It Unfeasible

$5.2 billion in taxpayer money has been spent to foster this technology in the US, yet the results are dismal. A recent government report found that of the 13 projects examined, eight had extended delays or financial problems, six were years behind schedule, and two had gone bankrupt.

3. Commercial Carbon Capture Unlikely by 2020

A study from Australian energy consultancy ACIL Talisman states that CCS will not be available in the short-term to generate electricity with low carbon emissions and that technology breakthroughs are still needed to make this technology feasible. The study does however find that concentrated solar, geothermal, and wind energy already are or will be in commercial use by 2020.

4. Unproven Technology

No commercial scale examples exist. The FutureGen plant in Illinois was to be the showcase for clean coal technology. A total of $50 million was spent, $40 million of which was federal funded. The price tag for the $1.8 billion plant had nearly doubled. The government pulled support for the project due to concern that costs would continue to climb.

5. Coal Mining is Very Harmful

The US averages 30 coal mining deaths annually, while China averages a staggering 8,000. Mountaintop removal mining, a method that is common in Appalachia, destroys ecosystems and has permanently buried over 1,200 miles of streams. Coal mining causes water pollution and lowers the quality of drinking water in neighboring communities. Unfortunately, clean coal technology does not address the many negative impacts of coal mining and could even require large amounts of coal to be mined because of the additional energy needed to sequester carbon emissions.

US climate fix could help solve financial crisis

If the US focused on curbing climate change as soon as a new president took office – or sooner – it could help pull the world from the financial brink, according to environmental policy experts.

"Skyrocketing energy prices and the financial crisis have been a wake-up call that something's got to change," says Cathy Zoi, chief executive officer of the Alliance for Climate Protection, which is chaired by former US vice president Al Gore.

"My very strong belief is that we need to reorient our investments toward this transition to a clean energy economy, and it will be the engine of growth for getting us out of the doldrums that we've gotten in right now," says Zoi.

The reorientation must include limits on emissions of climate-warming carbon in the US, she said: "Unless we take action at home, we're not going to be able to have much influence in the international arena about what gets done."

The Bush administration accepts that human-spurred climate change is a reality, but rejects mandatory across-the-board caps on carbon as a disadvantage when competing with fast-growing, big-emitting countries like China and India.

The US is alone among the major developed countries in staying out of the carbon-capping Kyoto protocol, but is part of international discussions on new targets to fight climate change, due to be finalised in Copenhagen at the end of 2009.

Both major US presidential candidates– Democrat Barack Obama and Republican John McCain – favour requiring reductions in greenhouse emissions, and environmental activists says whoever wins the White House in the 4 November elections will be an improvement over president George W Bush.

"There is an urgent need for whichever party wins the US election to give an early signal [of an intent to do more to combat global warming], or there cannot be a credible reason for 190 nations to come together in Copenhagen," says Achim Steiner, head of the UN Development Programme.

Rajendra Pachauri, who shared the 2007 Nobel Peace Price with Gore and who chairs the UN Intergovernmental Panel on Climate Change, says an Obama presidency would probably be more favourable to the fight against climate change.

But he adds: "Even if McCain wins, he has been very committed."

There is little chance of passing a US law to mandate a programme to cap and trade carbon emissions before Bush leaves office in January.

However, the first draft of a cap-and-trade bill was released this week by US Democratic representatives John Dingell of Michigan – home of the Big Three auto manufacturers – and Rick Boucher of Virginia – coal-mining country – that is likely to frame debate next year.

The draft legislation drew measured applause from environmental activists, who noted it contains options that could substantially weaken controls on greenhouse emissions from some sectors.

But the fact that these two law makers are crafting legislation aimed at curbing climate change indicates a possible change in tone in Washington.