The world's smallest steam engine

Though a steam engine the size of water droplet sounds like something out of a sci-fi novel, engineers from the University of Stuttgart have succeeded in developing such an engine. Built along the same lines as that of Robert Sterling’s steam engine invented almost 200 years ago this engineering marvel is just a few micrometers wide; and has a power output, which is significant keeping the size of the device in mind.

World's smallest steam engine

Robert Sterling’s engine was based on the cyclic expansion and contraction of a fluid to convert heat energy to mechanical work. The expansion and contraction of a fluid moved a piston in and out, to produce work and drive a wheel for example. Using this same concept, the engineers have effectively scaled down the engine to a much smaller size.

Design

The fluid of the Sterling engine has been replaced by a single colloid, a tiny bead of melamine plastic, which is in the micrometer range. This bead is placed on a surface of water, on which it floats. The device also utilizes a pair of optical infra-red lasers. One laser is associated with heating the water on which the colloid rests, while the other restricts the motion of the colloid. In effect, the laser resisting the movement of the melamine bead acts as the piston.

Working of the device

When the water is heated by a laser, the plastic expands. The laser is shut off, and the water is allowed to cool, in turn resulting in the contraction of the colloid. This cyclic expansion and contraction of the bead does work on the second laser field. This is how heat energy ends in the production of work.

Advantages

The main advantage without doubt is the size of the engine. The components of the device are relatively cheap, and this experiment should be a pioneer in the study of microscopic engines. Preliminary studies have also indicated that using a number of these micro engines instead of a normal sized one would give more mechanical output, and at the same time wastes produced would be significantly lower. In this day and age, where environmental pollution is a serious issue minimizing wastes are essential for a sustainable development.

Drawbacks

Where the size is a boon, it also creates some logistic problems. Though, scientists have proved that there are no issues regarding the violation of thermodynamic laws, at such small sizes, microscopic forces come into play, resulting in Brownian motion of the water droplets and the colloidal particle. Thus, the molecules of water jostle the colloid and losses in energy occur, sometimes making the engine stop altogether.

But the fact that this engine has come off the drawing board at all is a wonder. What is even more astounding is that the efficiency of the microscopic engine is comparable to that of a normal steam engine. This device will undoubtedly provide an important initial insight into the field of microscopic machines and will push the boundaries of knowledge to unknown levels!

Via: wired