World's Smallest Stirling Engine
World’s Smallest Stirling Engine

In this era of nanotechnology, from a transistor to a heat engine, everything is getting small. While reducing to micro size, we may think that the efficiency and performance of the device maybe compromised. However, researchers are trying their best to maintain the same ratings of a conventional device with its size being minimized.  Researchers from Stuttgart University and Max Planck Institute for Intelligent Systems have developed a micro particle that functions as a sterling engine (as small as 3 micrometers). A sterling engine is a heat engine in which gas expands and contracts there by moving the piston forward and backward. Sterling engine is an external combustion engine similar to the traditional steam engine. Sterling engine is more efficient than normal steam engines and is compactable with any heat source. In a sterling engine, the working gas is compressed in the cold section and is expanded in the hot section. A regenerative heat exchanger, which increases the efficiency of the sterling engine, distinguishes sterling engine from traditional steam engines.

This 200 year old design is highly efficient and has inspired researchers in developing a micro particle that works as a sterling engine. This invention, which will show the way to micro scale machinery, is a tremendous step in nanotechnology.  Researchers in Stuttgart made this nano-sterling engine by using a microscopic bead of malamine floating in water along with a couple of lasers.

When a machine is converted from its original size to its corresponding nanosize, a lot of technical difficulties may arise.  The laws, which are there in micro world and macro world, are different and hence there is much difficulty in making a nanomachine. Although there are many differences, some properties are there which are similar in both worlds. Researchers observe these similarities and make nanomachines. As many microscopic processes hinder the working of the nano engine, researchers were not been able to make the nano machine according to the same 200 year blue print designed by Robert Sterling. Some modifications were brought which has been explained in detail below. Nevertheless, the researchers were not only able to design a miniature prototype, but were also able to run it successfully.  Let us see how the 200 year old technology was accomplished in nanoscale.

The essential parts of the engine was replaced by Nano particles . Working gas and pistons are the two main components of a heat engine.  The working gas is an individually plastic bead measuring merely three micrometers, which is floating in water. As this particle is much larger than the size of the atom (about 10000 times larger), it can be observed using a microscope. In a conventional sterling engine, the pistons move backward and forward in a periodic motion. However, this is not possible in its nanoscale prototype, and thus they were replaced with laser beams. The intensity of the lasers can be varied periodically. The main objective of the heat engine is to compress and expand the gases with the help of a heat cylinder. The same procedure is developed in its corresponding nanoscale device by moving the colloidal particles with the help of laser sources.  A heat source is needed to maintain the heat difference for compression and expansion purposes. As this is done in nanoscale we cannot use a traditional coal source. This is replaced by a high power laser. The laser can heat the water and when the laser is turned off the water automatically loses temperature.

Compared to the macro version of the sterling engine this nanomachine will deliver more efficiency with minimal power input. Moreover, the energy produced by this device is known to be much more than its original version, even when it works under a full load. A specific application of this device is yet to be found, but the researchers believe that the device will follow all the basic thermodynamic laws even with its nanosize. The world will soon see the efficient use of highly reliable micro-machines.



  1. Ahmad Rami.

    That’s a great idea and i guess a very useful one with all this advantages, but can this be used with havey instruments like real cars and real big stuff?
    if yes then how can we put all the energy produced by several nano engines togather, in order to make them useful for the havey applications?