Scientists can coax tiny metal particles to self-assemble into microscopic wires that conduct electricity and repair themselves, new research reveals. Kevin D. Hermanson of the University of Delaware and his colleagues, who published their finding in the current issue of Science, suggest that such nanowires may prove useful for wet electronic and bioelectric circuits.
Image: copyright Science
The researchers placed particles of gold ranging in diameter from 15 to 30 nanometers in a fluid suspension within a thin chamber located between two electrodes. When an alternating voltage was applied to the electrodes, the particles first aggregated on the tip of one electrode and then started growing through the liquid toward the other electrode. The finding was quite surprising, team member Orlin Velev says, considering that "nothing was expected to happen with waterborne metallic nanoparticles in the AC electric field because the force between these tiny particles is so small." The wires assemble themselves and require no chemical reaction or soldering—a bonus in terms of miniaturization, Velev adds. Moreover, the scientists report, when the current became too high and caused the wires to burn out, they spontaneously repaired themselves. They also remained intact after the alternating voltage was removed.
The team next tried to manipulate the growth of the wire. Placing islands of conductive carbon paint in the gap between the electrodes, they found, resulted in the wire growing toward the islands and spanning the breach (see image). Such objects create a gradient in the electric field and influence the growth of the wire, the authors write. Other variables that affect wire growth include the strength of the electric field and the concentration of the particles, both of which must exceed a minimum value in order for the wire to self-assemble. "A promising aspect of this research," the authors conclude, "is the possibility to quickly and simply create electrical connections at ambient conditions in water environments."
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Controlling electronic current is essential to modern electronics, as data and signals are transferred by streams of electrons which are controlled at high speed. Demands on transmission speeds are also increasing as technology develops. Scientists from the Chair of Laser Physics and the Chair of Applied Physics at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have succeeded in switching on a current with a desired direction in graphene using a single laser pulse within a femtosecond ¬¬ – a femtosecond corresponds to the millionth part of a billionth of a second. This is more than a thousand times faster compared to the most efficient transistors today.
Graphene is up to the job
At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.
Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
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Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
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Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
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