Internal Combustion Microengine Has a Twist

By: 
April 15, 2014

As devices become smaller in size, so too must their power sources.

In today's world, we now have engines about the size of a softball that power some of the military's drones. Model helicopters, airplanes, and remote-controlled vehicles feature incredibly powerful combustion engines to propel them in the air and on the ground. However, could they be made smaller to power devices on a micro-scale?

There is one underlying issue with making internal combustion engines smaller in size, which boils down to inefficiency as heat leaks faster on surface areas and therefore generates less force. There are alternatives to power micro devices, such as MEMS or piezoelectric methods, but they are limited in scope and are often too slow to be a viable solution.

Those issues may be a thing of the past, as engineers from several institutions, led by Vitaly Svetovoy of the University of Twente in The Netherlands, have designed an internal combustion microengine that retains its efficiency at a size of only 100 microns x 100 microns x 5 microns

.

The engine was created using a tiny pressure chamber with a flexible membrane at one end and a pair of platinum electrodes at the other. A saltwater solution fills the pressure chamber and when an electrical current is introduced, it breaks the solution down to its basic components of oxygen and hydrogen, which form gaseous nano-bubbles. As the gases increase, they deform the membrane and thereby generate force. When the electrical current is turned off, the pressure drops and the membrane returns to its original shape, in almost the same way a piston functions in typical vehicle engines.

While the feat of creating a tiny combustion engine is incredible, the engineers are perplexed at exactly how the engine works. More specifically, what happens when the current is turned off and the pressure drops rapidly back to normal. It's apparently too fast for the gases to revert back into a liquid or diffuse out of the chamber; however, they do have a theory. They speculate that when the current is turned off, the nano-bubbles spontaneously combust (yes, you read that right) and turn back into a liquid, which would make it possible for the pressure to drop at a rapid rate. No matter how it functions, it will open up a new world of micro devices that could be run on one of the tiniest combustion engines ever created.

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