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

New X-ray camera will reveal big secrets about how chemistry works

Designed to record bursts of images at an unprecedented speed of 4.5 million frames per second, an innovative X-ray camera being built with STFC's world-class engineering expertise will help a major new research facility shed light on the structure of matter.

The unique device will be delivered to the billion-euro European XFEL (X-ray Free-Electron Laser) next year and will contribute to drug discovery and other vital research once this facility starts operating in 2015.

The go-ahead for continuation of the L3 million prototype collaboration contract for the camera's construction has been confirmed following a visit to STFC by a delegation from the European XFEL's Detector Advisory Committee.

The decision to entrust construction of this crucial piece of equipment to STFC recognises the organisation's outstanding capabilities in advanced microelectronics and the design of high-tech imaging devices (e.g. for the Large Hadron Collider at CERN).

Now under construction near Hamburg in Northern Germany, the European XFEL is a 2-mile-long facility that will use superconducting accelerator technology to accelerate electrons which then generate X-ray flashes a billion times brighter than those produced by conventional X-ray sources. Each flash will last less than one hundred million billionth of a second. With the properties of laser light, these short, intense flashes will, for example, make it possible to take three-dimensional X-ray images of single molecules.

Current leading-edge X-ray cameras are designed to capture images when matter is bombarded by a constant beam of X-rays. But the extreme brevity and intensity of the flashes produced by the European XFEL means such cameras will not be suitable for use at the new facility.

STFC's new device, which is being built in collaboration with University of Glasgow, is specifically designed to work in conjunction with hyper-short, hyper-brilliant X-ray flashes. It will be installed in one of the first experimental endstations incorporated in the European XFEL.

The device will help ensure that the European XFEL provides a unique opportunity for science and industry to understand matter and its behaviour, mapping the atomic details of viruses, for instance, or pinpointing the molecular composition of individual cells.

Dr Tim Nicholls of STFC says: "We're delighted that the European XFEL has turned to STFC to build this pioneering camera. It demonstrates how the UK can provide the high-tech excellence that world markets need, leading to scientific advances that make a real difference to people's lives."

Dr Markus Kuster, Group Leader of European XFEL GmbH's Detector Development says: "The European XFEL will represent a major step forward in equipping Europe with a new generation of research infrastructure that can meet the requirements of the 21st century. STFC's unique skills are creating an imaging device which will help this remarkable facility realise its vast potential".

Provided by Science and Technology Facilities Council (news : web)

Scientists identify how major biological sensor in the body works

A biological sensor is a critical part of a human cell's control system that is able to trigger a number of cell activities. A type of sensor known as the "gating ring" can open a channel that allows a flow of potassium ions through the cell's wall or membrane — similar to the way a subway turnstile allows people into a station. This flow of ions, in turn, is involved in the regulation of crucial bodily activities like blood pressure, insulin secretion and brain signaling.

But the biophysical functioning of the gating ring sensor has not been clearly understood. Now, UCLA researchers have uncovered for the first time the sensor's molecular mechanism, shedding new light on the complexity of cells' control systems.

The findings, published in the June 10 issue of the Journal of Biological Chemistry and featured as a "Paper of the Week," could lead to the development of specific therapies against diseases such as hypertension and genetic epilepsy.

Just as a smoke detector senses its environment and responds by emitting a sound signal, cells control their intracellular environment through molecular sensors that assess changes and trigger a response.

In this case, when calcium ions bind to the gating ring — which constitutes the intracellular part of an ionic channel known as the BK channel — the cell responds by allowing the flow of potassium ions across the cell membrane, with a wide range of consequences for the body.

BK channels are present in most cells in the body and regulate fundamental biological processes such as blood pressure, electrical signaling in the brain and nervous system, inner ear hair-tuning that impacts hearing, muscle contractions in the bladder, and insulin secretion from the pancreas, to name a few.

The UCLA researchers were able to identify for the first time how the gating ring is activated and how it rearranges itself to open the gateway that the ions flow through. Using state-of-the-art electrophysiological, biochemical and spectroscopic techniques in the laboratory, the team demonstrated that when calcium ions bind to the gating ring, its structure changes — that is, it converts the chemical energy of the calcium binding into mechanical work that facilitates the opening of the BK channel.

"We were able to resolve the biophysical changes occurring in the sensor, under conditions resembling those present inside a living cell, so we believe that these transformations reflect the molecular events occurring when BK channels operate in the body," said research team leader Riccardo Olcese, an associate professor in the department of anesthesiology's division of molecular medicine and a member of both the Cardiovascular Research Laboratory and Brain Research Institute at the David Geffen School of Medicine at UCLA.

"This is an exciting field of study and we hope that these findings will lead to a greater understanding of how this complex biological sensor operates," said study author Anoosh D. Javaherian, a research associate in the department of anesthesiology's division of molecular medicine division at the Geffen School of Medicine.

Javaherian added that only last year were the structures involved in the BK sensor even identified. This is the first study to demonstrate its function.

Since the BK channel and its sensor are involved in so many aspects of normal physiological function, researchers believe that it is likely the process could be implicated in many aspects of disease as well.

"This molecular and dynamic view of the BK intracellular sensor helps us understand how signaling molecules are sensed, providing new ideas on how to fight disease," said Taleh Yusifov, a research associate in the department of anesthesiology's division of molecular medicine at the Geffen School of Medicine.

For example, Yusifov noted, the malfunction of this BK channel's sensor has been associated with genetic epilepsy.

The next step in the research will assess if the BK gating ring sensor and channel are involved in sensing small molecules — other than calcium ions — which also have great biological significance in the workings of the human body.

Provided by University of California - Los Angeles

'Tall order' sunlight-to-hydrogen system works, neutron analysis confirms

 Researchers at the Department of Energy's Oak Ridge National Laboratory have developed a biohybrid photoconversion system -- based on the interaction of photosynthetic plant proteins with synthetic polymers -- that can convert visible light into hydrogen fuel.

Photosynthesis, the natural process carried out by plants, algae and some bacterial species, converts sunlight energy into chemical energy and sustains much of the life on earth. Researchers have long sought inspiration from photosynthesis to develop new materials to harness the sun's energy for electricity and fuel production.

In a step toward synthetic solar conversion systems, the ORNL researchers have demonstrated and confirmed with small-angle neutron scattering analysis that light harvesting complex II (LHC-II) proteins can self-assemble with polymers into a synthetic membrane structure and produce hydrogen.

The researchers envision energy-producing photoconversion systems similar to photovoltaic cells that generate hydrogen fuel, comparable to the way plants and other photosynthetic organisms convert light to energy.

"Making a, self-repairing synthetic photoconversion system is a pretty tall order. The ability to control structure and order in these materials for self-repair is of interest because, as the system degrades, it loses its effectiveness," ORNL researcher Hugh O'Neill, of the lab's Center for Structural Molecular Biology, said.

"This is the first example of a protein altering the phase behavior of a synthetic polymer that we have found in the literature. This finding could be exploited for the introduction of self-repair mechanisms in future solar conversion systems," he said.

Small angle neutron scattering analysis performed at ORNL's High Flux Isotope Reactor (HFIR) showed that the LHC-II, when introduced into a liquid environment that contained polymers, interacted with polymers to form lamellar sheets similar to those found in natural photosynthetic membranes.

The ability of LHC-II to force the assembly of structural polymers into an ordered, layered state -- instead of languishing in an ineffectual mush -- could make possible the development of biohybrid photoconversion systems. These systems would consist of high surface area, light-collecting panes that use the proteins combined with a catalyst such as platinum to convert the sunlight into hydrogen, which could be used for fuel.

The research builds on previous ORNL investigations into the energy-conversion capabilities of platinized photosystem I complexes -- and how synthetic systems based on plant biochemistry can become part of the solution to the global energy challenge.

"We're building on the photosynthesis research to explore the development of self-assembly in biohybrid systems. The neutron studies give us direct evidence that this is occurring," O'Neill said.

The researchers confirmed the proteins' structural behavior through analysis with HFIR's Bio-SANS, a small-angle neutron scattering instrument specifically designed for analysis of biomolecular materials.

"Cold source" neutrons, in which energy is removed by passing them through cryogenically chilled hydrogen, are ideal for studying the molecular structures of biological tissue and polymers.

The LHC-II protein for the experiment was derived from a simple source: spinach procured from a local produce section, then processed to separate the LHC-II proteins from other cellular components. Eventually, the protein could be synthetically produced and optimized to respond to light.

O'Neill said the primary role of the LHC-II protein is as a solar collector, absorbing sunlight and transferring it to the photosynthetic reaction centers, maximizing their output. "However, this study shows that LHC-II can also carry out electron transfer reactions, a role not known to occur in vivo," he said.

The research team, which came from various laboratory organizations including its Chemical Sciences Division, Neutron Scattering Sciences Division, the Center for Structural Molecular Biology and the Center for Nanophase Materials Sciences, consisted of O'Neill, William T. Heller, and Kunlun Hong, all of ORNL; Dimitry Smolensky of the University of Tennessee; and Mateus Cardoso, a former postdoctoral researcher at ORNL now of the Laboratio Nacional de Luz Sincrotron in Brazil.

"That's one of the nice things about working at a national laboratory. Expertise is available from a variety of organizations," O'Neill said.

The work, published in the journal Energy & Environmental Science, was supported with Laboratory-Directed Research and Development funding. HFIR is supported by the DOE Office of Science.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by DOE/Oak Ridge National Laboratory.

Journal Reference:

Mateus B. Cardoso, Dmitriy Smolensky, William T. Heller, Kunlun Hong, Hugh O'Neill. Supramolecular assembly of biohybrid photoconversion systems. Energy & Environmental Science, 2011; 4 (1): 181 DOI: 10.1039/C0EE00369G

Note: If no author is given, the source is cited instead.

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