Using a laser beam and a single element floating in
water, researchers at the University of Stuttgart and the Stuttgart-based Max
Planck Institute for Intelligent Systems built a steam engine measuring just
three thousandths of a millimetre - which sets the new world record for the
Smallest steam engine, according to World Records Academy
The Guinness world record for the smallest jet engine measures just 600nm across and weighs 1 femtogram (10^-15 kg). It was produced by Leibniz Institute Solid State Physics Dresden and demonstrated in Dresden, Germany.
Guinness World Records also documented the world record for the most poerful jet engine, set by a General Electric GE90-115B turbofan engine, which achieved steady state thrust of 568,927 N (127,900 lb) during final certification testing at Peebles, Ohio, USA.
Researcher Clemens Bechinger said: 'We've developed the world's smallest steam engine, or to be more precise the smallest Stirling engine.'
In the heat engine invented almost 200 years ago by Robert Stirling, a gas-filled cylinder is periodically heated and cooled so that the gas expands and contracts.
This makes a piston execute a motion with which it can drive a wheel, for example.
'We successfully decreased the size of the essential parts of a heat engine, such as the working gas and piston, to only a few micrometres and then assembled them to a machine,' adds researcher Valentin Blickle.
The working gas in the Stuttgart-based experiment thus no longer consisted of countless molecules, but of only one individual plastic bead measuring a mere three micrometres - one micrometre corresponds to one thousandth of a millimetre - which floated in water.
Since the particle is around 10,000 times larger than an atom, researchers could observe its motion directly in a microscope. The physicists replaced the piston, which moves periodically up and down in a cylinder, by a focused laser beam whose intensity is varied.
The optical forces of the laser limit the motion of the plastic particle to a greater and a lesser degree, like the compression and expansion of the gas in the cylinder of a large heat engine.
For the system to work properly, though, it must be heated during the expansion process from the outside, just like the boiler of a steam engine.
The researchers replaced the coal fire of an old-fashioned steam engine with a further laser beam that heats the water suddenly, but also lets it cool down as soon as it is switched off.
The physicists were astounded to discover that the machine converts as much energy per cycle on average and runs with the same efficiency as a normal sized heat engine.
'Our experiments provide us with an initial insight into the energy balance of a heat engine operating in microscopic dimensions. Although our machine does not provide any useful work as yet, there are no thermodynamic obstacles, in principle, which prohibit this in small dimensions,' says Bechinger.
