Monday, October 3, 2011

Proton-based transistor could let machines communicate with living things

Human devices, from light bulbs to iPods, send information using electrons. Human bodies and all other living things, on the other hand, send signals and perform work using ions or protons.

Materials scientists at the University of Washington have built a novel transistor that uses protons, creating a key piece for devices that can communicate directly with living things. The study is published online in the interdisciplinary journal Nature Communications.

Devices that connect with the human body's processes are being explored for biological sensing or for prosthetics, but they typically communicate using electrons, which are negatively charged particles, rather than protons, which are positively charged hydrogen atoms, or ions, which are atoms with positive or negative charge.

"So there's always this issue, a challenge, at the interface -- how does an electronic signal translate into an ionic signal, or vice versa?" said lead author Marco Rolandi, a UW assistant professor of materials science and engineering. "We found a biomaterial that is very good at conducting protons, and allows the potential to interface with living systems."

In the body, protons activate "on" and "off" switches and are key players in biological energy transfer. Ions open and close channels in the cell membrane to pump things in and out of the cell. Animals including humans use ions to flex their muscles and transmit brain signals. A machine that was compatible with a living system in this way could, in the short term, monitor such processes. Someday it could generate proton currents to control certain functions directly.

A first step toward this type of control is a transistor that can send pulses of proton current. The prototype device is a field-effect transistor, a basic type of transistor that includes a gate, a drain and a source terminal for the current. The UW prototype is the first such device to use protons. It measures about 5 microns wide, roughly a twentieth the width of a human hair.

"In our device large bioinspired molecules can move protons, and a proton current can be switched on and off, in a way that's completely analogous to an electronic current in any other field effect transistor," Rolandi said.

The device uses a modified form of the compound chitosan originally extracted from squid pen, a structure that survives from when squids had shells. The material is compatible with living things, is easily manufactured, and can be recycled from crab shells and squid pen discarded by the food industry.

First author Chao Zhong, a UW postdoctoral researcher, and second author Yingxin Deng, a UW graduate student, discovered that this form of chitosan works remarkably well at moving protons. The chitosan absorbs water and forms many hydrogen bonds; protons are then able to hop from one hydrogen bond to the next.

Computer models of charge transport developed by co-authors M.P. Anantram, a UW professor of electrical engineering, and Anita Fadavi Roudsari at Canada's University of Waterloo, were a good match for the experimental results.

"So we now have a protonic parallel to electronic circuitry that we actually start to understand rather well," Rolandi said.

Applications in the next decade or so, Rolandi said, would likely be for direct sensing of cells in a laboratory. The current prototype has a silicon base and could not be used in a human body. Longer term, however, a biocompatible version could be implanted directly in living things to monitor, or even control, certain biological processes directly.

The other co-author is UW materials science and engineering graduate student Adnan Kapetanovic. The research was funded by the University of Washington, a 3M Untenured Faculty Grant, a National Cancer Institute fellowship and the UW's Center for Nanotechnology, which is funded by the National Science Foundation.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by University of Washington. The original article was written by Hannah Hickey.

Journal Reference:

Chao Zhong, Yingxin Deng, Anita Fadavi Roudsari, Adnan Kapetanovic, M.P. Anantram, Marco Rolandi. A polysaccharide bioprotonic field-effect transistor. Nature Communications, 2011; 2: 476 DOI: 10.1038/ncomms1489

Scientists take first step towards creating 'inorganic life'

 Scientists at the University of Glasgow say they have taken their first tentative steps towards creating 'life' from inorganic chemicals potentially defining the new area of 'inorganic biology'.

Professor Lee Cronin, Gardiner Chair of Chemistry in the College of Science and Engineering, and his team have demonstrated a new way of making inorganic-chemical-cells or iCHELLs.

Prof Cronin said: "All life on earth is based on organic biology (i.e. carbon in the form of amino acids, nucleotides, and sugars, etc.) but the inorganic world is considered to be inanimate.

"What we are trying do is create self-replicating, evolving inorganic cells that would essentially be alive. You could call it inorganic biology."

The cells can be compartmentalised by creating internal membranes that control the passage of materials and energy through them, meaning several chemical processes can be isolated within the same cell -- just like biological cells.

The researchers say the cells, which can also store electricity, could potentially be used in all sorts of applications in medicine, as sensors or to confine chemical reactions.

The research is part of a project by Prof Cronin to demonstrate that inorganic chemical compounds are capable of self-replicating and evolving -- just as organic, biological carbon-based cells do.

The research into creating 'inorganic life' is in its earliest stages, but Prof Cronin believes it is entirely feasible.

Prof Cronin said: "The grand aim is to construct complex chemical cells with life-like properties that could help us understand how life emerged and also to use this approach to define a new technology based upon evolution in the material world -- a kind of inorganic living technology.

"Bacteria are essentially single-cell micro-organisms made from organic chemicals, so why can't we make micro-organisms from inorganic chemicals and allow them to evolve?

"If successful this would give us some incredible insights into evolution and show that it's not just a biological process. It would also mean that we would have proven that non carbon-based life could exist and totally redefine our ideas of design."

The paper is published in the journal Angewandte Chemie.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by University of Glasgow.

Journal Reference:

Geoffrey J. T. Cooper, Philip J. Kitson, Ross Winter, Michele Zagnoni, De-Liang Long, Leroy Cronin. Modular Redox-Active Inorganic Chemical Cells: iCHELLs. Angewandte Chemie International Edition, 2011; DOI: 10.1002/anie.201105068

Taming light: Mastering the fine structuring of ultrashort light fields

Physicists at the Max Planck Institute of Quantum Optics and LMU Munich have generated for the first time "white" light pulses. They are able to control their field on a time scale shorter than an optical oscillation. These new tools hold promise for unprecedented control of the motion of electrons.

An expedition through the fast-paced microscopic world of atoms reveals electrons that spin at enormous speeds and the gigantic forces that act on them. Monitoring the ultrafast motion of these electrons requires ultrashort flashes of light. However, in order to control them, the structure of these light flashes, or light pulses, needs to be tamed as well.

This type of control over light pulses has now been achieved, for the first time, by a team of physicists led by Dr. Eleftherios Goulielmakis and Professor Ferenc Krausz of the Laboratory of Attosecond Physics at the Max Planck Institute of Quantum Optics (MPQ) and Ludwig-Maximilians-Universität (LMU) in Munich, together with collaborators from the Center of Free-Electron Laser Science (DESY Hamburg) and the King Saud University (Saudi Arabia).

Taking advantage of the fact that light possesses both particle-like and wave-like properties, they have sculpted fine features into the waveform of these pulses of white light. Additionally, the researchers were able to make their pulses shorter than a complete light oscillation, thereby creating isolated sub-optical-cycle flashes of light for the first time. Not only will these novel tools allow for the precise control of electron motion in the fundamental building blocks of matter, they will also further our understanding of atomic processes and permit more precise timing of electronic processes in molecules and atoms.

The motion of electrons in the microcosm occurs on an attosecond time scale, where one attosecond is a billionth of a billionth of a second. On such a short scale, only light itself is able to keep up with the motion. Because of the fast oscillations of its own electromagnetic field, light can act on electrons rather like a pair of tweezers, influencing their motions and interactions. The time it takes light generated by modern laser sources to complete one full oscillation amounts to around 2.6 femtoseconds, where one femtosecond is 1000 attoseconds, or one millionth of a billionth of a second.

That is the reason why light is a promising tool for controlling electron dynamics in the microcosm. But before this can become reality, light's field oscillations have to be tamed, i.e. its electromagnetic field must be precisely and completely controllable on a time scale which is shorter than one complete oscillation cycle. In order to achieve this lofty aim, one first has to learn how to develop and perfect these extraordinary tweezers.

The international team assembled at MPQ and LMU Munich by Dr. Eleftherios Goulielmakis and Professor Ferenc Krausz has now taken a big step towards this ambitious goal, managing to sculpt the waveforms of laser pulses with sub-cycle precision. In order to control light pulses on a sub-cycle time scale, it is necessary to use white laser light, as it contains wavelengths (light colors) ranging from the near-ultraviolet through the visible all the way to the near infrared region of the electromagnetic spectrum.

The physicists have created these light pulses and sent them into a newly developed "light field synthesizer." The light field synthesizer is analogous to the sound synthesizers used by many musicians. Just as a sound synthesizer superimposes sound waves of different frequencies to create different sounds and beats, so the light field synthesizer superimposes optical waves of different colors and phases to create various field shapes. The apparatus first splits the incident white laser light into red, yellow and blue color channels. After manipulating the properties of the individual colors, these are recombined to form the synthesized wave form.

Several components of this novel device, e.g. its mirrors and its elaborate beam splitters, were developed in the service center of the Munich Center for Advanced Photonics (MAP) located at LMU. Utilizing this technology, the scientists were able to generate completely new isolated waveforms.

Furthermore, in doing so they managed to compose the shortest pulses ever measured in the visible spectral range, lasting only 2.1 femtoseconds. These pulses are more intense than those commonly afforded by current femtosecond light sources, because all the energy of the electromagnetic field is confined within a tiny temporal window. It is precisely these powerful and specially tailored electromagnetic forces which are necessary to control electrons in atoms and molecules, as they are similar in strength to the forces encountered in such microscopic systems.

However, to steer electron motion on a microscopic scale, strength is not the only prerequisite -- precision is also needed. The desired level of precision is provided by the well-controlled waveforms of the synthesized light pulses. Thanks to these latest results, the scientists have accomplished a major step towards the control of the microcosm. "These newly developed tools allow us to initiate, control and therefore further understand sub-atomic processes. With these devices, we can master the fine structuring of ultrashort light fields and reliably measure the newly formed light," explains Dr. Adrian Wirth, a Postdoctoral Fellow in the research team of Dr. Eleftherios Goulielmakis, leader of the ERC-research group "Attoelectronics."

As a matter of fact, the physicists have already applied this novel technique in an experiment. By shining the newly designed light pulses onto krypton atoms, the outermost electron was ripped away within less than 700 attoseconds, the fastest electronic process which has yet been initiated by visible light.

Similar processes can certainly be induced with similar precision in more complex systems such as molecules, solids and nanoparticles. This new technology may very well lead the way towards light-based electronics in the future. Light fields are expected to drive electrons not only in isolated systems such as atoms or molecules, but even on microscopic circuits so as to perform logic operations at unprecedented speeds" said Dr. Goulielmakis, whose group is exploring the principles of electronics on these extreme time scales. "We are progressively increasing our understanding of the principles in the microcosm and learning how to control it," adds Ferenc Krausz.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Ludwig-Maximilians-Universitaet Muenchen (LMU).

Journal Reference:

A. Wirth, M. T. Hassan, I. Grguras, J. Gagnon, A. Moulet, T. T. Luu, S. Pabst, R. Santra, Z. A. Alahmed, A. M. Azzeer, V. S. Yakovlev, V. Pervak, F. Krausz, E. Goulielmakis. Synthesized Light Transients. Science, 2011; DOI: 10.1126/science.1210268

Graphene may open the gate to future terahertz technologies

 Researchers from the University of Notre Dame in Indiana have harnessed another one of graphene's remarkable properties to better control a relatively untamed portion of the electromagnetic spectrum: the terahertz band.

Terahertz radiation offers tantalizing new opportunities in communications, medical imaging, and chemical detection. Straddling the transition between the highest energy radio waves and the lowest energy infrared light, terahertz waves are notoriously difficult to produce, detect, and modulate. Modulation, or varying the height of the terahertz waves, is particularly important because a modulated signal can carry information and is more versatile for applications such as chemical and biological sensing.

Some of today's most promising terahertz technologies are based on small semiconductor transistor-like structures that are able to modulate a terahertz signal at room temperature, which is a significant advantage over earlier modulators that could only operate at extremely cold temperatures.

Unfortunately, these transistor-like devices rely on a thin layer of metal called a "metal gate" to tune the terahertz signal. This metal gate significantly reduces the signal strength and limits how much the signal can be modulated to a lackluster 30 percent. As reported in the AIP's journal Applied Physics Letters, by replacing the metal gate with a single layer of graphene, the researchers have predicted that the modulation range can be significantly expanded to be in excess of 90 percent.

This modulation is controlled by applying a voltage between the graphene and semiconductor. Unlike the metal gate modulator, the graphene design barely diminished the output power of the terahertz energy. Made up of a one-atom-thick sheet of carbon atoms, graphene boasts a host of amazing properties: it's remarkably strong, a superb thermal insulator, a conductor of electricity, and now a better means to modulate terahertz radiation.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by American Institute of Physics.

Journal Reference:

Berardi Sensale-Rodriguez, Tian Fang, Rusen Yan, Michelle M. Kelly, Debdeep Jena, Lei Liu, Huili (Grace) Xing. Unique prospects for graphene-based terahertz modulators. Applied Physics Letters, 2011; 99 (11): 113104 DOI: 10.1063/1.3636435

Researchers make visible the structure of the smallest crystals

 A radical new way of making structures visible at the nano level has been developed at Johannes Gutenberg University Mainz (JGU). This new method makes it possible to determine with precision the arrangement of atoms and molecules in a diverse range of materials from cement to pharmaceuticals. The procedure, which is still in its infancy, comes from the field of electron microscopy and can resolve the structure of the tiniest crystals.

The method was developed by Dr. Ute Kolb's working group at the Institute of Physical Chemistry at Mainz University and is now receiving international attention. In cooperation with researchers from Spain and China, the method has now allowed the structure of a new type of fine-pore zeolite to be established, a study that the journal Science published in the end of August 2011. "We have opened a door to the world of nanostructures," is how Dr. Ute Kolb describes her working group's success.

The arrangement of atoms and molecules in a solid has a decisive influence on the physical properties of that material. Such structures were analyzed for the first time back in 1895 using X-rays, a method that has since become a standard procedure. The beginnings of the research in this area included the discovery in 1912 that crystals are made up of small grids, a characteristic that is responsible for the diversity of thermal, electrical, visual, and mechanical properties found in such substances. "The fact that this method had and still has a huge influence on our understanding of solids and their properties is reflected in the number of Nobel prizes awarded on the basis of structural analyses," says Kolb, describing the success story that is X-ray structural analysis.

In the age of nanotechnology, however, science is focusing increasingly on very small particles, which can no longer be captured by way of X-ray structural analysis. For example, an X-ray structural analysis of a single crystal is only possible up to a crystal size of around one micrometer, i.e. one thousandth of a millimeter. Below this threshold, in the sphere of nanostructures, electron diffraction tomography or automated diffraction tomography (ADT) allows scientists to make a similar determination of the structure of individual crystallites for the first time. "It is as if we have switched on a light in the world of nanostructures," says Kolb. As is the case with electron microscopy, the method is generally based on the concept of an electron beam being directed at an object and diffracted as a result. The diffraction behavior allows the location of the atoms to be established.

Together with her working group, Kolb has developed single-crystal electron diffraction tomography, to give it is full name, over the past 10 years. They had their first major success in 2009 with the determination of the structure of barium sulfate. "Since then, the number of materials whose structure we have been able to uncover has exploded," comments Kolb. The most recent example is the determination of the structure of the zeolite ITQ-43 in cooperation with Spanish and Chinese scientists. Zeolites are crystals that are created from a compound of aluminum and silicate. They have small pores which makes them interesting for the field of energy and environmental technology because of their potential use as adsorbers, ion exchangers or catalysts for example. In water treatment, they can help to filter out heavy metals; in the oil and gas industry, their introduction was like a mini revolution for crude oil cracking. We also encounter them in our everyday lives, in washing powders for instance. Avelino Corma and his team of researchers from the Technical University of Valencia synthesized a zeolite with small and medium-sized pores, the combination of which acts like a funnel, thereby enhancing its catalytic properties still further. How the complex crystal structure was analyzed using ADT is described by the team of researchers in their recent article in Science.

"The smaller the zeolite crystals are, the higher their catalytic efficiency," explains Kolb. With crystals the size of around 100 nanometers, which is similar to one eight-hundredth of a human hair, automated diffraction tomography is often the only way by which the structure can be fully and clearly resolved. "There is a large number of natural and synthetic solid materials for which our method may be used -- materials which are not available or cannot be manufactured in a suitable crystal size." So, over the past two years, Kolb has placed a wide range of materials under her microscope, from color pigments and titanate used in solar technology right up to minerals like charoite, a precious Russian gemstone.

In comparison with conventional electron microscopy characterizations, electron diffraction tomography is considerably faster, more accurate, and more complete. Whereas before, structures were researched for two years, using ADT a result can be obtained within just one day. Even beam-sensitive materials are, in principle, suitable for the method, which Kolb describes as "computer tomography for crystals." ADT also shares a characteristic with computer tomography that has played a major role in its success: the experimental sample under the electron microscope is gradually tipped over in order to gather data from a wide variety of different positions. Using this trick, scientists can avoid the key problem found in this area: the strong interaction of the electron beam with the sample has, up to now, made the electron diffraction much more difficult.

Since 2008, Dr. Ute Kolb has been Senior Lecturer at the Institute of Physical Chemistry and at the Center for High Resolution Electron Microscopy at Mainz University, concentrating on the field of electron crystallography. She presented her most recent work at a conference in Madrid in August 2011, where she was also elected to the Executive Committee of the Commission for Electron Crystallography of the International Union of Crystallography.

In order to advance the development of the method, the Mainz-based chemists are collaborating with Professor Dr. Elmar Schömer of the Institute of Computer Science as well as with Professor Dr. Thorsten Raasch of the Institute of Mathematics at Johannes Gutenberg University Mainz.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Universität Mainz.

Journal Reference:

J. Jiang, J. L. Jorda, J. Yu, L. A. Baumes, E. Mugnaioli, M. J. Diaz-Cabanas, U. Kolb, A. Corma. Synthesis and Structure Determination of the Hierarchical Meso-Microporous Zeolite ITQ-43. Science, 2011; 333 (6046): 1131 DOI: 10.1126/science.1208652