Tag: nanowires

The Future is Here: Smart Skin!

neuronsWhen it comes to modern research and development, biomimetics appear to be the order of the day. By imitating the function of biological organisms, researchers seek to improve the function of machinery to the point that it can be integrated into human bodies. Already, researchers have unveiled devices that can do the job of organs, or bionic limbs that use the wearer’s nerve signals or thoughts to initiate motion.

But what of machinery that can actually send signals back to the user, registering pressure and stimulation? That’s what researchers from the University of Georgia have been working on of late, and it has inspired them to create a device that can do the job of the largest human organ of them all – our skin. Back in April, they announced that they had successfully created a brand of “smart skin” that is sensitive enough to rival the real thing.

smart-skin_610x407In essence, the skin is a transparent, flexible arrays that uses 8000 touch-sensitive transistors (aka. taxels) that emit electricity when agitated. Each of these comprises a bundle of some 1,500 zinc oxide nanowires, which connect to electrodes via a thin layer of gold, enabling the arrays to pick up on changes in pressure as low as 10 kilopascals, which is what human skin can detect.

Mimicking the sense of touch electronically has long been the dream researchers, and has been accomplished by measuring changes in resistance. But the team at Georgia Tech experimented with a different approach, measuring tiny polarization changes when piezoelectric materials such as zinc oxide are placed under mechanical stress. In these transistors, then, piezoelectric charges control the flow of current through the nanowires.

nanowiresIn a recent news release, lead author Zhong Lin Wang of Georgia Tech’s School of Materials Science and Engineering said:

Any mechanical motion, such as the movement of arms or the fingers of a robot, could be translated to control signals. This could make artificial skin smarter and more like the human skin. It would allow the skin to feel activity on the surface.

This, when integrated to prosthetics or even robots, will allow the user to experience the sensation of touch when using their bionic limbs. But the range of possibilities extends beyond that. As Wang explained:

This is a fundamentally new technology that allows us to control electronic devices directly using mechanical agitation. This could be used in a broad range of areas, including robotics, MEMS, human-computer interfaces, and other areas that involve mechanical deformation.

prostheticNot the first time that bionic limbs have come equipped with electrodes to enable sensation. In fact, the robotic hand designed by Silvestro Micera of the Ecole Polytechnique Federale de Lausanne in Switzerland seeks to do the same thing. Using electrodes that connect from the fingertips, palm and index finger to the wearer’s arm nerves, the device registers pressure and tension in order to help them better interact with their environment.

Building on these two efforts, it is easy to get a glimpse of what future prosthetic devices will look like. In all likelihood, they will be skin-colored and covered with a soft “dermal” layer that is studded with thousands of sensors. This way, the wearer will be able to register sensations – everything from pressure to changes in temperature and perhaps even injury – from every corner of their hand.

As usual, the technology may have military uses, since the Defense Advanced Research Projects Agency (DARPA) is involved. For that matter, so is the U.S. Air Force, the U.S. Department of Energy, the National Science Foundation, and the Knowledge Innovation Program of the Chinese Academy of Sciences are all funding it. So don’t be too surprised if bots wearing a convincing suit of artificial skin start popping up in your neighborhood!

terminator2Source: news.cnet.com

Powered by the Sun: Nanotech Solar Cells

???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????With every passing year, interest in solar power has been growing by leaps and bounds. Given the impacts of Climate Change, widespread droughts, tropical storms, wildfires and increasing global temperatures, this should not come as a surprise. But an equally important factor in the adoption of clean energy alternatives has to do with improvements that are being made which will make it more efficient, accessible, and appealing to power companies and consumers.

Three such recent developments come to us from Standford, MIT, and the Neils Bohr Institute, respectively; where researchers have announced new ways using nanoprocesses to boost the yield of individual solar cells. In addition to cutting costs associated with production, installation, and storage, increasing the overall electrical yield of solar cells is a major step towards their full-scale implementation.

solar_nanoFirst, there’s MIT’s new concept for a solar cell, which uses nanowires to massively boost the efficiency of quantum dot photovoltaic cells. Quantum dots – which are basically nano-sized crystals of a semiconducting material – are already being considered as an alternative to conventional silicon cells, since they are cheaper and easier to produce.

However, until recently they have been a letdown in the efficiency department, lagging significantly behind their silicon counterparts. By merging zinc oxide nanowires into the design of their quantum dot photovoltaic cells, the MIT researchers were able to boost the current produced by 50%, and overall efficiency by 5%.  Ultimately, their goal is to get that up to 10%, since that is considered to be the threshold for commercial adoption.

gallium-arsenide-nanowire-solar-cellMeanwhile, researchers at the Niels Bohr Institute in Denmark and EPFL in Switzerland announced that they have built solar cells out of single nanowires. In this case, the process involved growing gallium-arsenide (GaAs) wires on a silicon substrate, and then completing the circuit with a transparent indium tin oxide electrode, which are currently employed in the creation of photovoltaic cells and LEDs on the market today.

Prior to these development, nanowires were being researched mainly in conjunction with computer chips as a possible replacement for silicon. But thanks to the combined work of these researchers, we may very well be looking at solar cells which are not only hair-thin (as with the kind being developed by Penn State University) but microscopically thin. And much like the research at the University of Oslo involving the use of microbeads, this too will mean the creation of ultra-thin solar cells that have a massive energy density – 180 mA/cm2, versus ~40 mA/cm2 for crystalline silicon PVs.

solar_boosterAnd last, but not least, there was the announcement from Stanford University of a revolutionary new type of solar cell that has doubled the efficiency of traditional photovoltaic cells. This new device uses a process called photon-enhanced thermionic emission (PETE) that allows for the absorption of not only light, but heat. This combination makes this new type of cell the equivalent of a turbocharged solar panel!

pete-photovoltaic-thermionic-diagram-stanfordIn conventional cells, photons strike a semiconductor (usually silicon), creating electricity by knocking electrons loose from their parent atoms. The PETE process, on the other hand, uses the gallium arsenide wafer on top gather as much sunlight as possible, creating a lot of excited electrons using the photovoltaic effect. The underside, which is composed of nanoantennae, emits these photoexcited electrons across a vacuum to the anode with gathers them and turns them into an electrical current.

Beneath the anode is a of heat pipe that collects any leftover heat which could be used elsewhere. One of the easiest applications of PETE would be in concentrating solar power plants, where thousands of mirrors concentrate light on a central vat of boiling water, which drives a steam turbine. By concentrating the light on PETE devices instead, Stanford estimates that their power output could increase by 50%, bringing the cost of solar power generation down into the range of fossil fuels.

Though there are still kinks in their design – the cell has a very low 2% rate of energy efficient thus far – the researchers at Stanford are making improvements which are increasing its efficiency exponentially. And although their planned upgrades should lead to a solar cell capable of operating in extremely hot environments, they stress that the goal here is to build one that is capable of gathering power in non-desert environments, such as Spaced-Based solar arrays.

Combined with improved production methods, storage capacities, and plans to mount solar arrays in a variety of new places (such as on artificial islands), we could be looking at the wholesale adoption of solar power within a few years time. Every day, it seems, new methods are being unveiled that will allow Solar to supplant fossil fuels as the best, cheapest and most efficient means of energy production. If all goes as planned, all this could be coming just in time to save the planet, fingers crossed!

Sources: Extremetech.com, (2)