How To Purify Water Without Wasting Energy

Amid the coronavirus pandemic, people in developed countries are assured of ample supplies of clean water to wash their hands as often as needed to protect themselves from the virus. And yet, nearly a third of the world’s population is not even assured of clean water for drinking. University of Rochester researchers have now found a way to address this problem by using sunlight—a resource that everyone can access—to evaporate and purify contaminated water with greater than 100 percent efficiency.

How is this possible? In a paper in Nature Sustainability, researchers in the laboratory of Chunlei Guo, professor of optics, demonstrate how a burst of femtosecond laser pulses etch the surface of a normal sheet of aluminum into a superwicking (water-attracting), super energyabsorbing material. Using sunlight to boil has long been recognized as a way to eliminate microbial pathogens and reduce deaths from diarrheal infections. But boiling water does not eliminate heavy metals and other contaminants. Experiments by the lab show that their new method reduces the presence of all common contaminants, such as detergent, dyes, urine, heavy metals, and glycerin, to safe levels for drinking.

Solar-based water purification can greatly reduce contaminants because nearly all the impurities are left behind when the evaporating water becomes gaseous and then condenses and gets collected. The most common method of solar-based water evaporation is volume heating, in which a large volume of water is heated but only the top layer can evaporate. This is obviously inefficient, Guo says, because only a small fraction of the heating energy gets used. A more efficient approach, called interfacial heating, places floating, multilayered absorbing and wicking materials on top of the water, so that only water near the surface needs to be heated. But the available materials all have to float horizontally on top of the water and cannot face the sun directly. Furthermore, the available wicking materials become quickly clogged with contaminants left behind after evaporation, requiring frequent replacement of the materials.

The panel developed by the Guo lab avoids these inefficiencies by pulling a thin layer of water out of the reservoir and directly onto the solar absorber surface for heating and evaporation. “Moreover, because we use an open-grooved surface, it is very easy to clean by simply spraying it,” Guo says.

The biggest advantage,” he adds, “is that the angle of the panels can be continuously adjusted to directly face the sun as it rises and then moves across the sky before setting” —maximizing energy absorption. “There was simply nothing else resembling what we can do here,” Guo says.

Source: https://www.rochester.edu/

Photonic Chips

Emitting light from silicon has been the ‘Holy Grail’ in the microelectronics industry for decades. Solving this puzzle would revolutionize computing, as chips will become faster than ever. Researchers from Eindhoven University of Technology  (TU-e) now succeeded: they have developed an alloy with silicon that can emit light. The team will now start creating a silicon laser to be integrated into current chips.

Every year we use and produce significantly more data. But our current technology, based on electronic chips, is reaching its ceiling. The limiting factor is heat, resulting from the resistance that the electrons experience when traveling through the copper lines connecting the many transistors on a chip. If we want to continue transferring more and more data every year, we need a new technique that does not produce heat. Bring in photonics, which uses photons (light particles) to transfer data. In contrast to electrons, photons do not experience resistance. As they have no mass or charge, they will scatter less within the material they travel through, and therefore no heat is produced. The energy consumption will therefore be reduced. Moreover, by replacing electrical communication within a chip by optical communication, the speed of on-chip and chip-to-chip communication can be increased by a factor 1000. Data centers would benefit most, with faster data transfer and less energy usage for their cooling system. But these photonic chips will also bring new applications within reach. Think of laser-based radar for self-driving cars and chemical sensors for medical diagnosis or for measuring air and food quality.

To use light in chips, you will need a light source; an integrated laser. The main semiconductor material that computer chips are made of is silicon. But bulk silicon is extremely inefficient at emitting light, and so was long thought to play no role in photonics. Thus, scientists turned to more complex semiconductors, such as gallium arsenide and indium phosphide. These are good at emitting light but are more expensive than silicon and are hard to integrate into existing silicon microchips.

To create a silicon compatible laser, scientists needed to produce a form of silicon that can emit light. That’s exactly what researchers from Eindhoven University of Technology (TU/e) now succeeded in. Together with researchers from the universities of Jena, Linz and Munich, they combined silicon and germanium in a hexagonal structure that is able to emit light. A breakthrough after 50 years of work.

Nanowires with hexagonal silicon-germanium shells

The crux is in the nature of the so-called band gap of a semiconductor,” says lead researcher Erik Bakkers from TU/e. “If an electron ‘drops’ from the conduction band to the valence band, a semiconductor emits a photon: light.” But if the conduction band and valence band are displaced with respect to each other, which is called an indirect band gap, no photons can be emitted – as is the case in silicon. “A 50-year old theory showed however that silicon, alloyed with germanium, shaped in a hexagonal structure does have a direct band gap, and therefore potentially could emit light,” explains Bakkers.

Shaping silicon in a hexagonal structure, however, is not easy. As Bakkers and his team master the technique of growing nanowires, they were able to create hexagonal silicon in 2015. They realized pure hexagonal silicon by first growing nanowires made from another material, with a hexagonal crystal structure. Then they grew a silicon-germanium shell on this template. Elham Fadaly, shared first author of the study: “We were able to do this such that the silicon atoms are built on the hexagonal template, and by this forced the silicon atoms to grow in the hexagonal structure.” But they could not yet make them to emit light, until now. Bakkers team managed to increase the quality of the hexagonal silicon-germanium shells by reducing the number of impurities and crystal defects. When exciting the nanowire with a laser, they could measure the efficiency of the new material. Alain Dijkstra, also shared first author of the study and responsible for measuring the light emission: “Our experiments showed that the material has the right structure, and that it is free of defects. It emits light very efficiently.”

The findings have been published in the journal Nature.

Source: https://www.tue.nl/

Laser Method Turns Any Metal Surface Into A Bacteria Killer

Bacterial pathogens can live on surfaces for days. What if frequently touched surfaces such as doorknobs could instantly kill them offPurdue University engineers have created a laser treatment method that could potentially turn any metal surface into a rapid bacteria killer – just by giving the metal’s surface a different texture. In a study published in the journal Advanced Materials Interfaces, the researchers demonstrated that this technique allows the surface of copper to immediately kill off superbugs such as MRSA.

A laser prepares to texture the surface of copper, enhancing its antimicrobial properties

Copper has been used as an antimicrobial material for centuries. But it typically takes hours for native copper surfaces to kill off bacteria,” said Rahim Rahimi, a Purdue assistant professor of materials engineering. “We developed a one-step laser-texturing technique that effectively enhances the bacteria-killing properties of copper’s surface.”

The technique is not yet tailored to killing viruses such as the one responsible for the COVID-19 pandemic, which are much smaller than bacteria. Since publishing this work, however, Rahimi’s team has begun testing this technology on the surfaces of other metals and polymers that are used to reduce risks of bacterial growth and biofilm formation on devices such as orthopedic implants or wearable patches for chronic wounds.

Source: https://www.purdue.edu/

Manipulating The “Boss Gene” For Reprogramming Humans

 

It seems like everything is going wireless these days. That now includes efforts to reprogram the human genome. A new University at Buffalo-led study describes how researchers wirelessly controlled FGFR1 — a gene that plays a key role in how humans grow from embryos to adults — in lab-grown brain tissue. The ability to manipulate the gene, the study’s authors say, could lead to new cancer treatments, and ways to prevent and treat mental disorders such as schizophrenia.

It represents a step forward toward genetic manipulation technology that could upend the treatment of cancer, as well as the prevention and treatment of schizophrenia and other neurological illnesses. It centers on the creation of a new subfield of research the study’s authors are calling “optogenomics,” or controlling the human genome through laser light and nanotechnology.

The left image shows the gene FGFR1 in its natural state. The right image shows the gene when exposed to laser light, which causes the gene to activiate and deactivate.

The potential of optogenomic interfaces is enormous,” says co-author Josep M. Jornet, PhD, associate professor in the Department of Electrical Engineering in the UB School of Engineering and Applied Sciences. “It could drastically reduce the need for medicinal drugs and other therapies for certain illnesses. It could also change how humans interact with machines.

For the past 20 years, scientists have been combining optics and genetics — the field of optogenetics — with a goal of employing light to control how cells interact with each other. By doing this, one could potentially develop new treatments for diseases by correcting the miscommunications that occur between cells. While promising, this research does not directly address malfunctions in genetic blueprints that guide human growth and underlie many diseases. The new research begins to tackle this issue because FGFR1 — it stands for Fibroblast Growth Factor Receptor 1 — holds sway over roughly 4,500 other genes, about one-fifth of the human genome, as estimated by the Human Genome Project, says study co-author Michal K. Stachowiak.

In some respects, it’s like a boss gene,” says Stachowiak, PhD, professor in the Department of Pathology and Anatomical Sciences in the Jacobs School of Medicine and Biomedical Sciences at UB. “By controlling FGFR1, one can theoretically prevent widespread gene dysregulations in schizophrenia or in breast cancer and other types of cancer.”

The work — spearheaded by UB researchers Josep M. Jornet, Michal K. Stachowiak, Yongho Bae and Ewa K. Stachowiak — was reported in the June edition of the Proceedings of the Institute of Electrical and Electronics Engineers.

Source: http://www.buffalo.edu/

Chinese ‘Death Star’ For Submarines

China is developing a satellite with a powerful laser for anti-submarine warfare that researchers hope will be able to pinpoint a target as far as 500 metres below the surface. It is the latest addition to the country’s expanding deep-sea surveillance programme, and aside from targeting submarines – most operate at a depth of less than 500 metres – it could also be used to collect data on the world’s oceansProject Guanlan, meaning “watching the big waves”, was officially launched in May at the Pilot National Laboratory for Marine Science and Technology in Qingdao, Shandong. It aims to strengthen China’s surveillance activities in the world’s oceans, according to the laboratory’s website.

Scientists are working on the satellite’s design at the laboratory, but its key components are being developed by more than 20 research institutes and universities across the country. Song Xiaoquan, a researcher involved in the project, said if the team can develop the satellite as planned, it will make the upper layer of the seamore or less transparent”. “It will change almost everything,” Song said.

While light dims 1,000 times faster in water than in the air, and the sun can penetrate no more than 200 metres below the ocean surface, a powerful artificial laser beam can be 1 billion times brighter than the sun. But this project is ambitious – naval researchers have tried for more than half a century to develop a laser spotlight for hunting submarines using technology known as light detection and ranging (lidar). In theory, it works like this – when a laser beam hits a submarine, some pulses bounce back. They are then picked up by sensors and analysed by computer to determine the target’s location, speed and three-dimensional shape.

But in real life, lidar technology can be affected by the device’s power limitations, as well as cloud, fog, murky water – and even marine life such as fish and whales. Added to that, the laser beam deflects and scatters as it travels from one body of water to another, making it more of a challenge to get a precise calculation. Experiments carried out by the United States and former Soviet Union achieved maximum detection depths of less than 100 metres, according to openly available information. That range has been extended in recent years by the US in research funded by Nasa and the Defence Advanced Research Projects Agency (DARPA).

Source: https://www.scmp.com/

How To Manipulate And Move Cells With Light

Wits physicists demonstrate a new device for manipulating and moving tiny objects with light. When you shine a beam of light on your hand, you don’t feel much, except for a little bit of heat generated by the beam. When you shine that same light into a world that is measured on the nano– or micro scale, the light becomes a powerful manipulating tool that you can use to move objects around – trapped securely in the light.

Researchers from the Structured Light group from the School of Physics at the University of the Witwatersrand in Johannesburg, South Africa, have found a way to use the full beam of a laser light, to control and manipulate minute objects such as single cells in a human body, tiny particles in small volume chemistry, or working on future on-chip devices. While the specific technique, called holographic optical trapping and tweezing, is not new, the Wits Researchers found a way to optimally use the full force of the light – including vector light that was previously unavailable for this application. This forms the first vector holographic trap.

CLICK ON THE IMAGE TO ENJOY THE VIDEO

Previously holographic traps were limited to particular classes of light (scalar light), so it is very exciting that we can reveal a holistic device that covers all classes of light, including replicating all previous trapping devices,” explains Professor Andrew Forbes, team leader of the collaboration and Distinguished Professor in the School of Physics where he heads up the Wits Structured Light Laboratory.

What we have done is that we have demonstrated the first vector holographic optical trapping and tweezing system. The device allows micrometer sized particles, such as biological cells, to be captured and manipulated only with light.”

Source: https://www.wits.ac.za/

A Wearable Device For Regrowing Hair

Although some people embrace the saying “bald is beautiful,” for others, alopecia, or excessive hair loss, can cause stress and anxiety. Some studies have shown that stimulating the skin with lasers can help regrow hair, but the equipment is often large, consumes lots of energy and is difficult to use in daily life. Now, researchers have developed a flexible, wearable photostimulator that speeds up hair growth in mice. 

Affecting millions of men and women worldwide, alopecia has several known causes, including heredity, stress, aging and elevated male hormones. Common treatments include medications, such as minoxidil, corticosteroid injections and hair transplant surgery. In addition, irradiating the bald area with a red laser can stimulate hair follicles, causing cells to proliferate. However, this treatment is often impractical for home use. So, Keon Jae Lee and colleagues wanted to develop a flexible, durable photostimulator that could be worn on human skin.

Shaved mice with flexible vertical LEDs (f-VLEDs) regrows hair faster than no treatment (Con) or minoxidil injections (MNX)

The team fabricated an ultrathin array of flexible vertical micro-light-emitting diodes (mLEDs). The array consisted of 900 red mLEDs on a chip slightly smaller than a postage stamp and only 20 mm thick. The device used almost 1,000 times less power per unit area than a conventional phototherapeutic laser, and it did not heat up enough to cause thermal damage to human skin. The array was sturdy and flexible, enduring up to 10,000 cycles of bending and unbending. The researchers tested the device’s ability to regrow hair on mice with shaved backs. Compared with untreated mice or those receiving minoxidil injections, the mice treated with the mLED patch for 15 minutes a day for 20 days showed significantly faster hair growth, a wider regrowth area and longer hairs.

The findings are reported in ACS Nano.

Source: https://www.acs.org/

Climate Change: How To Forecast Changes In Weather More Accurately

Europe is launching  a satellite this week that will use new laser technology to measure the winds sweeping across Earth and help scientists forecast changes in weather more accurately.

The Aeolus mission will provide scientists with data on winds in remote areas, such as over oceans, that they have not been able to get from weather balloons, ground stations and airplanes but which are crucial to predicting changes in weather.

Forecasting is of course still limited, but then we will certainly be able to understand the processes better that lead to extreme weather phenomena,” Paolo Ferri, the European Space Agency’s (ESA) head of mission operations, told  ahead of the launch.

Many scientists warn that global warming will result in more frequent and intense heatwaves, precipitation and storms, causing billions of euros in damage and costing thousands of human lives every year.

Better weather forecasts will allow scientists to warn the population when hurricanes are heading their way and predict weather patterns such as El Niño, which can cause crop damage, fires and flash floods.

The Aeolus mission – named after a character of Greek mythology who was appointed keeper of the winds – is scheduled to blast off from Europe’s space port in Kourou, French Guiana

Source: https://www.reuters.com/

Colorful 3D Printing

People are exploring the use of 3D printing for wide-ranging applications, including manufacturing, medical devices, fashion and even food. But one of the most efficient forms of 3D printing suffers from a major drawback: It can only print objects that are gray or black in color. Now, researchers have tweaked the method so it can print in all of the colors of the rainbow.

THIS BRIGHTLY COLORED DRAGON WAS PRODUCED BY 3D PRINTING, USING GOLD NANORODS AS PHOTOSENSITIZERS.

Selective laser sintering (SLS) printers use a laser to heat specific regions of a powdered material, typically nylon or polyamide, so that the powder melts or sinters to form a solid mass. The printer adds then selectively sinters new powdered material layer by layer until the desired 3D structure is obtained. To reduce the energy requirements of the process, researchers have added compounds called photosensitizers to the polymer powders. These materials, such as carbon nanotubes, carbon black and graphene, absorb light much more strongly than the polymers and transfer heat to them, enabling the use of cheaper, lower-power lasers. However, the carbon-based photosensitizers can only produce printed objects that are gray or black. Gerasimos Konstantatos, Romain Quidant and their coworkers at The Institute of Photonic Sciences (IFCO) wanted to find a photosensitizer that would enable color printing by the SLS method.

The researchers designed gold nanorods to strongly absorb in the near-infrared region of the spectrum while being almost transparent to visible light. They coated them with silica and then mixed them with polyamide powders to print 3D objects. They found that the gold nanorods were much better at converting light from the laser to heat than carbon black, the industry standard. Also, the new photosensitizers could produce much whiter and — when mixed with dyes — brightly colored 3D objects. Importantly, the materials are cost-effective for large-scale production. The researchers have filed several patent applications related to the new technology.

The findings are reported in the ACS journal Nano Letters.

Source: https://www.acs.org/

A stamp-sized nanofilm stores more data than 200 DVDs

Ninety percent of the world’s data has been created in the last two years, with a massive 2.5 quintillion bytes generated every single day. As you might suspect, this causes some challenges when it comes to storage. While one option is to gradually turn every square inch of free land into giant data centers, researchers from the  Center for Advanced Optoelectronic Functional Material Research, Northeast Normal University (China) may have come up with a more elegant solution. In a potential breakthrough, they have developed a new nanofilm80 times thinner than a human hair — that is able to store large amounts of data holographically. A single 10-by-10 cm piece of this film could archive more than 1,000 times the amount of data found on a DVD. By our count, that means around 8.5 TB of data. This data can also be retrieved incredibly quickly, at speeds of up to 1GB per second: The equivalent of 20 times the reading speed of modern flash memory.

In the journal Optical Materials Express, the researchers detail the fabrication process of the new film. This involves using a laser to write information onto silver nanoparticles on a titanium dioxide (titania) semiconductor film. This stores the data in the form of 3D holograms, thereby allowing it to be compressed into smaller spaces than regular optical systems.

That’s exciting enough, but what really makes the work promising is the fact that the data is stored in a way that is stable. Previous attempts at creating films for holographic data storage have proven less resilient than alternate storage methods since they can be wiped by exposure to ultraviolet light. That makes them less-than-viable options for long-term information storage. The creators of this new film, however, have shown that it has a high stability even in the presence of such light. This environmental stability means that the device could be used outside — or even conceivably in harsher radiation conditions like outer space.

Going forward, the researchers aim to test their new film by putting it through its paces outdoors. Should all go according to plan, it won’t be too long before this is available on the market. We might be willing to throw down a few bucks on Kickstarter for a piece!

Source: https://www.osapublishing.org
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