Researchers develop new microengine, but aren't sure how it works

Researchers develop new microe...
At the microscopic level, combustion can't support itself, as it does in this Petri dish filled with ethanol (Image: Kyanite)
At the microscopic level, combustion can't support itself, as it does in this Petri dish filled with ethanol (Image: Kyanite)
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At the microscopic level, combustion can't support itself, as it does in this Petri dish filled with ethanol (Image: Kyanite)
At the microscopic level, combustion can't support itself, as it does in this Petri dish filled with ethanol (Image: Kyanite)

If you’re going to do something like building a Porsche 911 that fits on the head of a pin, or make a microscopic medical pump, you need a microscopic engine. A team of researchers from the University of Twente in the Netherlands, the Russian Academy of Sciences, and Germany’s University of Freiburg have developed a micro-engine that burns oxygen and hydrogen, but there’s a small problem; they’re not sure how the thing works.

Making micro machines means making micro power plants, and with nanotechnology advancing by the day, it's a wonder that they aren't more common. Micro-engines are cheaper to produce than conventional ones, they can do things that larger engines cannot, and they could help their larger cousins operate more efficiently. The problem is that making an engine that is small, powerful, and fast is more elusive than first thought.

The main hurdle to be overcome is building a motor or actuator that can change energy into motion. Getting energy to a micro-machine in the form of electricity is simple enough, but the tricky bit is getting that electricity to do any useful work.

This is due to the problem of scale. Electric motors as they scale down generate less and less force. Combustion engines have an even worse time, because on a microscopic scale the small space of a combustion chamber with its comparatively large surface area carries heat away too fast, so combustion can’t be supported. Though there are alternatives, such as electroactive polymers and electrochemical actuators, these are limited in function and too slow to be practical.

The new 100 x 100 x 5 μm3 micro-engine is made of layers of polymer membrane 530 nanometers thick. It uses electrodes generating an alternating current to break down water into hydrogen and oxygen, in a chamber formed in the membrane. As the gases mix, they spontaneously combust. As they do so, the electric pulses are switched off momentarily, producing more power in a sort of piston-stroke effect.

That’s all well and good, but it’s also a bit embarrassing because the researchers aren’t at all sure how the engine works – more specifically, they aren't sure how the combustion is able to occur. It’s a bit like the famous bumblebee quandary; the maths says the bee shouldn't be able to fly, but it does.

Though the mystery has yet to be solved, the scientists think that it might be due to transitional nanobubbles less than 200 nm in diameter that form for fractions of a second in the chamber, that prevent heat from dissipating so combustion can occur. The researchers say that this may be counterintuitive, but these bubbles have already demonstrated such counterintuitive properties.

The scientists believe that if the details of how the engine operates can be worked out, it opens up the great potential of micromachines for future development.

Source: Science Reports

Roger Garrett
Hydrogen and Oxygen do NOT spontaneously combust.
There will be "spontaneous" combustion in the presence of a catalyst such as platinum. This has been used for decades in lead-acid batteries to prevent build up of hydrogen. (Google "Catalytic Battery Cap"). As the H2 gas passes over the catalyst it recombines with ambient oxygen to produce water which reduces the need to service the batteries. The catalytic material is not affected in the process and remains behind. Perhaps there was a minute quantity of some catalytic material in the system which assisted with combustion.
Mel Tisdale
It is a bit confusing that it uses AC to produce oxygen and hydrogen by the process of electrolysis. I would have thought that was impossible.
however it works, this is one more step towards my idea of making nano robots to mine the asteroids.
The hydrogen anion react exothermically with a proton releasing heat and diatomic hydrogen. The condition to oxidize hydrogen back to water is acomplished. What they not observed is a ground somewhere in that cell. I developed a larger scale hydrogen generator on AC and three electrodes and in some conditions with 20 watts and despite flow of water the cell overheat confident space the system can be that engine...
Luke Cummings
It is in fact well understood how the bumble bee can fly, that math cannot explain it is a common myth:
Larry Hooten
Nikola Tesla knew how it operates. That momentary switch-off mentioned in the article is very similar to the radiant impulse energy he was experimenting with after AC power had been accepted. We're close to developing the Free Energy so feared by George Westinghouse.
These "nano bubbles" sound a lot like Water cavitation. There is a form of HO gas which is combustible, and it's not surprising that they're creating this unknowingly from their use of electrolysis in their process. The combustible form of water vapor has a different pattern than that of evaporated water. Evaporated water looks the same as water on the molecular level[ H-O-H beside H-O-H]. However, cavitated water vapor creates a ring where two Oxygens share one hyrdogen, and two hydrogen share one oxygen. [H-O-H-O-H-O-H-O-H-O but in a circle] When it forms and then comes into contact with an electrical current, it's probably what's causing the explosion. Water cavitation is often seen in Pistol shrimp, but scientists have no idea how it works. There's a whole wave of experimenting going on with it in people developing "free energy" machines. This article is an unwitting testament of how effective and possible it is.