Micromotors Race About By Turning Water Into Hydrogen Gas 85
MTorrice writes "Microscopic particles of aluminum and gallium rocket around using water as their fuel. The particles, which are 20 micrometers in diameter, are asymmetric: A chemical reaction on the back side of the particle forms hydrogen gas bubbles that propel the motor forward. Over the past several years, bioengineers have built micro- and nanosized rockets that zip through liquids, fueled by chemical reactions between the materials that make up the rockets and their environments. The engineers hope someday these tiny motors could help deliver cargo, such as drugs, in people. Unfortunately, many of these motors require toxic hydrogen peroxide as fuel source, limiting their use in the body. To overcome that constraint, the new micromotors harness a well-known reaction between aluminum and water to produce hydrogen gas."
Re:20m in diameter (Score:5, Informative)
Slashdot's lack of unicode support strikes again! There should have been a mu there, oops.
Re:so... (Score:4, Informative)
Read TFA - or heck, even just the /. blurb, and you'll see aluminum is consumed in the reaction to produce hydrogen. It's not free energy.
Re:Where has the Oxygen gone to ? (Score:5, Informative)
Aluminum oxide byproduct.
I've been familiar with this reaction for awhile. You can see youtube videos of it. Gallium is expensive but can be recycled from the waste making the process a fairly reasonable method of transporting energy in a lightweight, and compact way.
This is a clever application and I will keep it in mind as a "gas generator", rocket, or source of pneumatic pressure.
Aluminium is the fuel, not water (Score:5, Informative)
argh, again this kind of misleading headline that makes the people who only read the headline think a perpetual machine is finally invented.
The energy comes from aluminium, aluminium "burning" into aluminium-oxide.
Putting the "converting water into hydrogen" into headline is misleading reporting.
can't tell if you're serious (Score:5, Informative)
Why do you think it kills the germs in a cut?
Toxic yes, hazardous less so (Score:5, Informative)
Notice how it foams up as soon as it hits blood? Blood is full of peroxidase. Breaking down hydrogen peroxide into water and oxygen is routine housekeeping, since your body actually produces hydrogen peroxide as a weapon for the immune system to use.
So: toxic, but gets detoxified almost instantly, and anyway wouldn't it be in the equivalent of a fuel tank?
Re:Hydrogen fuel-Looking forward to the car (Score:4, Informative)
Besides harmless emissions from hydrogen, the cost of fuel will be extremely low compared to gasoline.
Only if the cost of the electricity used to hydrolyze the water is also extrememly low. For the foreseeable future, the only viably-large source of electricity that is close to carbon neutral will likely be nuclear power - sun and wind likely won't be sufficient for a long time. Also, power from sun, wind, and fission are currently priced artificially higher than power from oil, because with oil we're 'borrowing' from future generations to support our extravagant lifestyle but aren't even calculating the principal, never mind the interest...
I'm all in favour of building 'hydrogen economy' vehicles and infrastructure right now, even though it's not yet clear exactly how we'll come up with enough clean energy to justify it, unless we go all-out nuclear, the prospect of which scares the sh*t out of me. But let's be VERY clear that in the short term we may in fact be increasing carbon emissions by doing so. There are WAY too many people out there who see zero emissions at the tailpipe and think the problem is solved, when in fact total emissions per mile driven may well be higher than those produced by a gasoline engine. Joe Public needs to be educated about such things, and the makers of various 'environmentally friendly' technologies aren't about to do that if it risks harming their sales. We in the tech and scientific communities have an obligation to start getting the word out that There Ain't No Such Thing As A Free Lunch.
Re:Hydrogen fuel (Score:5, Informative)
The only way to cheaply make H2 for fuel is to use substances which start off with high Gibbs free energies. You're probably familiar with many of them - methane, propane, various petroleum products, as well as alcohols and sugars/wood. Converting these substances to H2 for fuel is pretty much the same as burning them in an internal combustion engine, except with additional intermediate steps and huge storage, transportation,and delivery complications. There's an advantage in that there's no pesky carbon, nitrogen, and sulfur in the second step (hydrogen -> water) so we don't get CO2, nitrous oxides, and sulfides as byproducts. But you still need to deal with those byproducts in the first step (fuel -> hydrogen). So it's questionable whether the tradeoff is worth it.
Incidentally, this is why many people refer to hydrogen as a battery, not a fuel. Raw hydrogen gas is pretty much non-existent on this planet. So you're not getting free energy from the hydrogen. You're taking energy from other sources (burning coal or petroleum, nuclear, hydro, wind, solar) and storing it by converting something into hydrogen gas, then releasing that energy when you burn the hydrogen (well, releasing what's left after efficiency losses). Any energy calculation of the hydrogen economy has to take into account the efficiency losses due to this multi-step conversion process. It's almost bad enough to knock a hydrogen fuel cell car's efficiency down to the efficiency of an ICE gasoline car. (60% efficient fuel cell * 60% efficient hydrolysis = 36% efficiency. Modern ICEs are close to 30% efficient.)
In TFA's case, the energy used to convert aluminum oxide into metallic aluminum is used to liberate the H2 from the H2O (the Al being converted to Al2O3 by the extra oxygen in the process). So it's almost certainly wasting more energy than if you just did straight electrolysis on the water. The only benefit is that aluminum is very compact and easy to handle as a fuel source, much more so than hydrogen or storing electricity in a battery.
Re:Followup question: Why doesnt my bike do the sa (Score:4, Informative)
Actually aluminium does rust. But unlike iron rust, aluminium oxyde produces a solid and stable surface