World's smallest steam engine: Heat engine measuring only a few micrometers works as well as its larger counterpart, although it sputters

 What would be a case for the repair shop for a car engine is completely normal for a micro engine. If it sputters, this is caused by the thermal motions of the smallest particles, which interfere with its running. Researchers at the University of Stuttgart and the Stuttgart-based Max Planck Institute for Intelligent Systems have now observed this with a heat engine on the micrometre scale. They have also determined that the machine does actually perform work, all things considered. Although this cannot be used as yet, the experiment carried out by the researchers in Stuttgart shows that an engine does basically work, even if it is on the microscale. This means that there is nothing, in principle, to prevent the construction of highly efficient, small heat engines.

A technology which works on a large scale can cause unexpected problems on a small one. And these can be of a fundamental nature. This is because different laws prevail in the micro- and the macroworld. Despite the different laws, some physical processes are surprisingly similar on both large and small scales. Clemens Bechinger, Professor at the University of Stuttgart and Fellow of the Max Planck Institute for Intelligent Systems, and his colleague Valentin Blickle have now observed one of these similarities.

"We've developed the world's smallest steam engine, or to be more precise the smallest Stirling engine, and found that the machine really does perform work," says Clemens Bechinger. "This was not necessarily to be expected, because the machine is so small that its motion is hindered by microscopic processes which are of no consequence in the macroworld." The disturbances cause the micromachine to run rough and, in a sense, sputter.

The laws of the microworld dictated that the researchers were not able to construct the tiny engine according to the blueprint of a normal-sized one. 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," says Valentin Blickle. The working gas in the Stuttgart-based experiment thus no longer consists 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 floats in water. Since the colloid particle is around 10,000 times larger than an atom, researchers can 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 periodically 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. The particle then does work on the optical laser field. In order for the contributions to the work not to cancel each other out during compression and expansion, these must take place at different temperatures. This is done by heating the system from the outside during the expansion process, 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 fact that the Stuttgart machine runs rough is down to the water molecules which surround the plastic bead. The water molecules are in constant motion due to their temperature and continually collide with the microparticle. In these random collisions, the plastic particle constantly exchanges energy with its surroundings on the same order of magnitude as the micromachine converts energy into work. "This effect means that the amount of energy gained varies greatly from cycle to cycle, and even brings the machine to a standstill in the extreme case," explains Valentin Blickle. Since macroscopic machines convert around 20 orders of magnitude more energy, the tiny collision energies of the smallest particles in them are not important.

The physicists are all the more astonished that the machine converts as much energy per cycle on average despite the varying power, and even runs with the same efficiency as its macroscopic counterpart under full load. "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 Clemens Bechinger. This is surely good news for the design of reliable, highly efficient micromachines.

The above story is reprinted from materials provided by Max-Planck-Gesellschaft.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Valentin Blickle and Clemens Bechinger. Realization of a micrometre-sized stochastic heat engine. Nature Physics, 11 December 2011 DOI: 10.1038/NPHYS2163

A 'check engine' light for the human body?

Imagine a sensor implanted in your body that signals when you're getting sick -- almost like the "check engine" light in a car. That scenario sounds like pure fantasy, but it may be closer to reality than many people think, according to an article in the current edition of Chemical & Engineering News (C&EN), ACS' weekly newsmagazine.

In the article, C&EN Associate Editor Britt E. Erickson describes one such medical device that's heading for clinical trials, perhaps later in 2011. It is a robotic arm that moves almost like a natural arm, thanks to a control system that monitors brain activity via a biosensor implanted on the surface of a patient's brain. That project aims to provide better artificial arms for wounded soldiers.

The article describes how scientists and medical device regulators are working together to fast track approval of such "biosensors" and devices. Biosensors monitor changes in the body, often "disease markers" — proteins, genes and other biochemical substances involved in health and disease. And they raise a red flag when things go awry. CEN points out that scientific advances will be important in tapping the full potential of biosensors. Scientists must find new disease markers, for instance, and better materials for making biosensors so they work for long periods while implanted in the body.

More information: "Biosensors on the Fast Track". This story is available at http://pubs.acs.or … 911gov2.html

Provided by American Chemical Society (news : web)

DNA engine observed in real-time traveling along base pair track

 In a complex feat of nanoengineering, a team of scientists at Kyoto University and the University of Oxford have succeeded in creating a programable molecular transport system, the workings of which can be observed in real time. The results, appearing in the latest issue of Nature Nanotechnology, open the door to the development of advanced drug delivery methods and molecular manufacturing systems.

Resembling a monorail train, the system relies on the self-assembly properties of DNA origami and consists of a 100 nm track together with a motor and fuel. Using atomic force microscopy (AFM), the research team was able to observe in real time as this motor traveled the full length of the track at a constant average speed of around 0.1 nm/s.

"The track and motor interact to generate forward motion in the motor," explained Dr. Masayuki Endo of Kyoto University's Institute for Integrated Cell-Material Sciences (iCeMS). "By varying the distance between the rail 'ties,' for example, we can adjust the speed of this motion."

The research team, including lead author Dr. Shelley Wickham at Oxford, anticipates that these results will have broad implications for future development of programable molecular assembly lines leading to the creation of synthetic ribosomes.

"DNA origami techniques allow us to build nano- and meso-sized structures with great precision," elaborated iCeMS Prof. Hiroshi Sugiyama. "We already envision more complex track geometries of greater length and even including junctions. Autonomous, molecular manufacturing robots are a possible outcome."

The article was published online in the February 6, 2011 issue of Nature Nanotechnology.

Funding for this research was provided by the Engineering and Physical Sciences Research Council (EP/G037930/1), the Clarendon Fund, the Oxford-Australia Scholarship Fund, the CREST program of the Japan Science and Technology Agency (JST), and the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT).

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Institute for Integrated Cell-Material Sciences, Kyoto University, via EurekAlert!, a service of AAAS.

Journal Reference:

Shelley F. J. Wickham, Masayuki Endo, Yousuke Katsuda, Kumi Hidaka, Jonathan Bath, Hiroshi Sugiyama, Andrew J. Turberfield. Direct observation of stepwise movement of a synthetic molecular transporter. Nature Nanotechnology, 2011; DOI: 10.1038/nnano.2010.284

Nanotechnology used to prolong machine and engine life

Guojun Liu has discovered a way to use nanotechnology to reduce friction in automobile engines and machines.

"The technology should be useful in a wide range of machineries other than automobile engines," says Dr. Liu, a professor in the Department of Chemistry and an expert in polymer synthesis. "If implemented industrially, this nanotechnology should help prolong machine life and improve energy efficiency."

Dr Liu's team prepared miniscule polymer particles that were only tens of nanometers in size. These particles were then dispersed in automobile engine base oils. When tested under metal surface contact conditions that simulated conditions found in automobile engines, these tiny particles were discovered to have an unprecedented friction reduction capability.

Even at a low concentration, the nanoparticles performed much better than the friction additive that is currently used by many industries. They were able to reduce friction by 55 per cent more than the currently achievable rate.

Dr. Liu's discovery has earned the Society of Tribologists and Lubrication Engineers' Captain Alfred E. Hunt Memorial Award.

This is the first research that Dr. Liu has done in the field of friction reduction and lubrication.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Queen's University.