How To Forge Graphene In 3D Shape

The wonder material graphene gets many of its handy quirks from the fact that it exists in two dimensions, as a sheet of carbon only one atom thick. But to actually make use of it in practical applications, it usually needs to be converted into a 3D form. Now, researchers have developed a new and relatively simple way to do just that, using lasers to “forge” a three-dimensional pyramid out of graphene.

This isn’t the first time graphene has been given an extra dimension. In 2015, researchers from the University of Illinois molded graphene into 3D structures by layering it onto shaped substrates, and early this year MIT scientists found that tubes of the stuff could be shaped into 3D coral-like structures 10 times stronger than steel but just five percent as dense. Rice University researchers have also recently made graphene foam and reinforced it with carbon nanotubes.

But this new technique, developed by researchers in Finland and Taiwan, might be an easier and faster method to make 3D graphene. By focusing a laser onto a fine point on a 2D graphene lattice, the graphene at that spot is irradiated and bulges outwards. A variety of three-dimensional shapes can be made by writing patterns with the laser spot, with the height of the shape controlled by adjusting the irradiation dose at each particular point.

The team illustrated that technique by deforming a sheet of graphene into a 3D pyramid, standing 60 nm high. That sounds pretty tiny, but it’s 200 times taller than the graphene sheet itself.

We call this technique optical forging, since the process resembles forging metals into 3D shapes with a hammer,” says Mika Pettersson, co-author of the study. “In our case, a laser beam is the hammer that forges graphene into 3D shapes. The beauty of the technique is that it’s fast and easy to use; it doesn’t require any additional chemicals or processing. Despite the simplicity of the technique, we were very surprised initially when we observed that the laser beam induced such substantial changes on graphene. It took a while to understand what was happening.”

The researchers initially assumed that the laser had “doped” the graphene, introducing impurities into the material, but after further examination they found that wasn’t the case.

When we first examined the irradiated graphene, we were expecting to find traces of chemical species incorporated into the graphene, but we couldn’t find any,” comments Wei Yen Woon, co-author of the study. “After some more careful inspections, we concluded that it must be purely structural defects, rather than chemical doping, that are responsible for such dramatic changes on graphene.

The scientists explain that the optically forged graphene is structurally sound, highlighting its potential for building 3D architectures out of the material for a wide range of applications. In this form, the graphene has different electronic and optical properties from its 2D counterpart.

The research was published in the journal Nano Letters.

Source: Academy of Finland

Dialysis Membrane Made From Graphene

Dialysis, in the most general sense, is the process by which molecules filter out of one solution, by diffusing through a membrane, into a more dilute solution. Outside of hemodialysis, which removes waste from blood, scientists use dialysis to purify drugs, remove residue from chemical solutions, and isolate molecules for medical diagnosis, typically by allowing the materials to pass through a porous membrane.

Today’s commercial dialysis membranes separate molecules slowly, in part due to their makeup: They are relatively thick, and the pores that tunnel through such dense membranes do so in winding paths, making it difficult for target molecules to quickly pass through.

Now MIT engineers have fabricated a functional dialysis membrane from a sheet of graphene — a single layer of carbon atoms, linked end to end in hexagonal configuration like that of chicken wire. The graphene membrane, about the size of a fingernail, is less than 1 nanometer thick. (The thinnest existing memranes are about 20 nanometers thick.) The team’s membrane is able to filter out nanometer-sized molecules from aqueous solutions up to 10 times faster than state-of-the-art membranes, with the graphene itself being up to 100 times faster.

While graphene has largely been explored for applications in electronics, Piran Kidambi, a postdoc in MIT’s Department of Mechanical Engineering, says the team’s findings demonstrate that graphene may improve membrane technology, particularly for lab-scale separation processes and potentially for hemodialysis.

Because graphene is so thin, diffusion across it will be extremely fast,” Kidambi says. “A molecule doesn’t have to do this tedious job of going through all these tortuous pores in a thick membrane before exiting the other side. Moving graphene into this regime of biological separation is very exciting.”

Kidambi is a lead author of a study reporting the technology, published today in Advanced Materials. Six co-authors are from MIT, including Rohit Karnik, associate professor of mechanical engineering, and Jing Kong, associate professor of electrical engineering.

Source: http://news.mit.edu/

New Material Ten Times Stronger Than Steel, Designed From Graphene

A team of researchers at MIT has designed one of the strongest lightweight materials known, by compressing and fusing flakes of graphene, a two-dimensional form of carbon. The new material, a sponge-like configuration with a density of just 5 percent, can have a strength 10 times that of steel. In its two-dimensional form, graphene is thought to be the strongest of all known materials. But researchers until now have had a hard time translating that two-dimensional strength into useful three-dimensional materials.

The new findings show that the crucial aspect of the new 3-D forms has more to do with their unusual geometrical configuration than with the material itself, which suggests that similar strong, lightweight materials could be made from a variety of materials by creating similar geometric features.

graphene material

The team was able to compress small flakes of graphene using a combination of heat and pressure. This process produced a strong, stable structure whose form resembles that of some corals and microscopic creatures called diatoms. These shapes, which have an enormous surface area in proportion to their volume, proved to be remarkably strong. “Once we created these 3-D structures, we wanted to see what’s the limit — what’s the strongest possible material we can produce,” says Zhao Qin, research scientist at MIT. To do that, they created a variety of 3-D models and then subjected them to various tests. In computational simulations, which mimic the loading conditions in the tensile and compression tests performed in a tensile loading machine, “one of our samples has 5 percent the density of steel, but 10 times the strength,” Qin says.
The findings have been reported in the journal Science Advances.

Source: http://news.mit.edu/

How To Turn Plants Into Bomb-Sniffing Machines

Spinach is no longer just a superfood: By embedding leaves with carbon nanotubes, MIT engineers have transformed spinach plants into sensors that can detect explosives and wirelessly relay that information to a handheld device similar to a smartphone. This is one of the first demonstrations of engineering electronic systems into plants, an approach that the researchers call “plant nanobionics”.

spinach-detects-bombsCLICK ON THE IMAGE TO ENJOY THE VIDEO

The goal of plant nanobionics is to introduce nanoparticles into the plant to give it non-native functions,” says Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT and the leader of the research team.

In this case, the plants were designed to detect chemical compounds known as nitroaromatics, which are often used in landmines and other explosives. When one of these chemicals is present in the groundwater sampled naturally by the plant, carbon nanotubes embedded in the plant leaves emit a fluorescent signal that can be read with an infrared camera. The camera can be attached to a small computer similar to a smartphone, which then sends an email to the user.

This is a novel demonstration of how we have overcome the plant/human communication barrier,” says Strano, who believes plant power could also be harnessed to warn of pollutants and environmental conditions such as drought.

Strano is the senior author of a paper describing the nanobionic plants in  Nature Materials. The paper’s lead authors are Min Hao Wong, an MIT graduate student who has started a company called Plantea to further develop this technology, and Juan Pablo Giraldo, a former MIT postdoc who is now an assistant professor at the University of California at Riverside.

Michael McAlpine, an associate professor of mechanical engineering at the University of Minnesota, says this approach holds great potential for engineering not only sensors but many other kinds of bionic plants that might receive radio signals or change color. “When you have manmade materials infiltrated into a living organism, you can have plants do things that plants don’t ordinarily do,” says McAlpine, who was not involved in the research. “Once you start to think of living organisms like plants as biomaterials that can be combined with electronic materials, this is all possible.”

In the 2014 plant nanobionics study, Strano’s lab worked with a common laboratory plant known as Arabidopsis thaliana. However, the researchers wanted to use common spinach plants for the latest study, to demonstrate the versatility of this technique. “You can apply these techniques with any living plant,” Strano says. So far, the researchers have also engineered spinach plants that can detect dopamine, which influences plant root growth, and they are now working on additional sensors, including some that track the chemicals plants use to convey information within their own tissues. “Plants are very environmentally responsive,” Strano says. “They know that there is going to be a drought long before we do. They can detect small changes in the properties of soil and water potential. If we tap into those chemical signaling pathways, there is a wealth of information to access.”

These sensors could also help botanists learn more about the inner workings of plants, monitor plant health, and maximize the yield of rare compounds synthesized by plants such as the Madagascar periwinkle, which produces drugs used to treat cancer. “These sensors give real-time information from the plant. It is almost like having the plant talk to us about the environment they are in,” Wong says. “In the case of precision agriculture, having such information can directly affect yield and margins.”

Source: http://news.mit.edu/

NonCarbon SuperCapacitor Produces More Power

Energy storage devices called supercapacitors have become a hot area of research, in part because they can be charged rapidly and deliver intense bursts of power. However, all supercapacitors currently use components made of carbon, which require high temperatures and harsh chemicals to produce. Now researchers at MIT and elsewhere have for the first time developed a supercapacitor that uses no conductive carbon at all, and that could potentially produce more power than existing versions of this technology.

mit-supercapacitor

We’ve found an entirely new class of materials for supercapacitors,” Dincă says.

Dincă and his team have been exploring for years a class of materials called metal-organic frameworks, or MOFs, which are extremely porous, sponge-like structures. These materials have an extraordinarily large surface area for their size, much greater than the carbon materials do. That is an essential characteristic for supercapacitors, whose performance depends on their surface area. But MOFs have a major drawback for such applications: They are not very electrically conductive, which is also an essential property for a material used in a capacitor.

One of our long-term goals was to make these materials electrically conductive,” Dincă says, even though doing so “was thought to be extremely difficult, if not impossible.” But the material did exhibit another needed characteristic for such electrodes, which is that it conducts ions (atoms or molecules that carry a net electric charge) very well.

All double-layer supercapacitors today are made from carbon,” Dincă says. “They use carbon nanotubes, graphene, activated carbon, all shapes and forms, but nothing else besides carbon. So this is the first noncarbon, electrical double-layer supercapacitor.”

The team’s findings are being reported in the journal Nature Materials, in a paper by Mircea Dincă, an MIT associate professor of chemistry; Yang Shao-Horn, the W.M. Keck Professor of Energy; and four others.

Source: http://news.mit.edu/

How To Safely Use Graphene Implants Into Tissues

In the future, our health may be monitored and maintained by tiny sensors and drug dispensers, deployed within the body and made from grapheneone of the strongest, lightest materials in the world. Graphene is composed of a single sheet of carbon atoms, linked together like razor-thin chicken wire, and its properties may be tuned in countless ways, making it a versatile material for tiny, next-generation implants. But graphene is incredibly stiff, whereas biological tissue is soft. Because of this, any power applied to operate a graphene implant could precipitously heat up and fry surrounding cells.

Now, engineers from MIT and Tsinghua University in Beijing have precisely simulated how electrical power may generate heat between a single layer of graphene and a simple cell membrane. While direct contact between the two layers inevitably overheats and kills the cell, the researchers found they could prevent this effect with a very thin, in-between layer of water. By tuning the thickness of this intermediate water layer, the researchers could carefully control the amount of heat transferred between graphene and biological tissue. They also identified the critical power to apply to the graphene layer, without frying the cell membrane.

Co-author Zhao Qin, a research scientist in MIT’s Department of Civil and Environmental Engineering (CEE), says the team’s simulations may help guide the development of graphene implants and their optimal power requirements.

graphene2014

We’ve provided a lot of insight, like what’s the critical power we can accept that will not fry the cell,” Qin says. “But sometimes we might want to intentionally increase the temperature, because for some biomedical applications, we want to kill cells like cancer cells. This work can also be used as guidance [for those efforts.

Qin’s co-authors include Markus Buehler, head of CEE and the McAfee Professor of Engineering, along with Yanlei Wang and Zhiping Xu of Tsinghua University.
The results are published today in the journal Nature Communications.

Source: http://news.mit.edu/

Vaccine That Is Programmable In One Week

MIT engineers have developed a new type of easily customizable vaccine that can be manufactured in one week, allowing it to be rapidly deployed in response to disease outbreaks. So far, they have designed vaccines against Ebola, H1N1 influenza, and Toxoplasma gondii (a relative of the parasite that causes malaria), which were 100 percent effective in tests in mice. The vaccine consists of strands of genetic material known as messenger RNA, which can be designed to code for any viral, bacterial, or parasitic protein. These molecules are then packaged into a molecule that delivers the RNA into cells, where it is translated into proteins that provoke an immune response from the host.

In addition to targeting infectious diseases, the researchers are using this approach to create cancer vaccines that would teach the immune system to recognize and destroy tumors.

MIT-Program-Vaccines_0 (1)

This nanoformulation approach allows us to make vaccines against new diseases in only seven days, allowing the potential to deal with sudden outbreaks or make rapid modifications and improvements,” says Daniel Anderson, an associate professor in MIT’s Department of Chemical Engineering and a member of MIT’s Koch Institute for Integrative Cancer Research and Institute for Medical Engineering and Science (IMES).

Anderson is the senior author of a paper describing the new vaccines in the Proceedings of the National Academy of Sciences. The project was led by Jasdave Chahal, a postdoc at MIT’s Whitehead Institute for Biomedical Research, and Omar Khan, a postdoc at the Koch Institute; both are the first authors of the paper.

Source: http://news.mit.edu/

How To Map RNA Molecules In The Brain

Cells contain thousands of messenger RNA molecules, which carry copies of DNA’s genetic instructions to the rest of the cell. MIT engineers have now developed a way to visualize these molecules in higher resolution than previously possible in intact tissues, allowing researchers to precisely map the location of RNA throughout cells. Key to the new technique is expanding the tissue before imaging it. By making the sample physically larger, it can be imaged with very high resolution using ordinary microscopes commonly found in research labs.

MIT RNA-Imaging

Now we can image RNA with great spatial precision, thanks to the expansion process, and we also can do it more easily in large intact tissues,” says Ed Boyden, an associate professor of biological engineering and brain and cognitive sciences at MIT, a member of MIT’s Media Lab and McGovern Institute for Brain Research, and the senior author of a paper describing the technique in the July 4 issue of Nature Methods.

Studying the distribution of RNA inside cells could help scientists learn more about how cells control their gene expression and could also allow them to investigate diseases thought to be caused by failure of RNA to move to the correct location.

Source: http://news.mit.edu/

Solar Cells: How To Transform More Solar Energy Into Electricity

Sagrario Domínguez-Fernández, a Spanish telecommunications engineer at CEMITEC, has managed to increase light absorption in silicon by means of nanostructures etched onto photovoltaic cells. This increases the efficiency obtained in these electronic devices which are made of this element and which transform solar energy into electricity.
solar cells

Over 30 percent of the sunlight that strikes a silicon is reflected, which means it cannot be used in the photoelectric conversion,” explained Sagrario Domínguez. “Because the nanostructures on the surface of a material have dimensions in the light wavelength range, they interfere with the surface in a particular way and allow the amount of reflected light to be modified.”

Sagrario Domínguez designed and optimised structures on a nanometric scaleto try and find one that would minimise the reflectance [ability of a surface to reflect light] of the silicon in the wavelength range in which solar cells function.” In their manufacturing process, she resorted to what is known as laser interference lithography which consists of applying laser radiation to a photo-sensitive material to create structures on a nanometric scale. Specifically, she used polished silicon wafers to which she gave the shape of cylindrical pillar and obtained a 77 percent reduction in the reflectance of this element.

Sagrario Domínguez then went on to modify the manufacturing processes to produce the nanostructures on the silicon substrates used in commercial solar cells. “These substrates have dimensions and a surface roughness that makes them, ‘a priori’, unsuitable for processes,” pointed out the researcher. Having overcome the difficulties, she incorporated nanostructures onto following the standard processes of the photovoltaics industry. “According to the literature, this is the first time that it has been possible to manufacture periodic nanostructures; they are the ones that on the surface of a material are continuously repeated on substrates of this type, and therefore, the first standard solar cell with periodic nanostructures,” pointed out the new MIT PhD holder. The efficiency obtained is 15.56 percent, which is a very promising value when compared with others included in the literature.

Source: http://phys.org/

Bones and Shells, Inspiration For New Materials

Researchers at MIT are seeking to redesign concrete — the most widely used human-made material in the world — by following nature’s blueprints. In a paper published online in the journal Construction and Building Materials, the team contrasts cement pasteconcrete’s binding ingredient — with the structure and properties of natural materials such as bones, shells, and deep-sea sponges. As the researchers observed, these biological materials are exceptionally strong and durable, thanks in part to their precise assembly of structures at multiple length scales, from the molecular to the macro, or visible, level.

From their observations, the team, led by Oral Buyukozturk, a professor in MIT’s Department of Civil and Environmental Engineering (CEE), proposed a new bioinspired, “bottom-upapproach for designing cement paste.

bones molecular structure

These materials are assembled in a fascinating fashion, with simple constituents arranging in complex geometric configurations that are beautiful to observe,” Buyukozturk says. “We want to see what kinds of micromechanisms exist within them that provide such superior properties, and how we can adopt a similar building-block-based approach for concrete.”

Ultimately, the team hopes to identify materials in nature that may be used as sustainable and longer-lasting alternatives to Portland cement, which requires a huge amount of energy to manufacture. “If we can replace cement, partially or totally, with some other materials that may be readily and amply available in nature, we can meet our objectives for sustainability,” Buyukozturk says.

Source: http://news.mit.edu/2016/

Obesity: How To Burn Fat

Researchers at MIT and Brigham and Women’s Hospital have developed nanoparticles that can deliver antiobesity drugs directly to fat tissue. Overweight mice treated with these nanoparticles lost 10 percent of their body weight over 25 days, without showing any negative side effects. The drugs work by transforming white adipose tissue, which is made of fat-storing cells, into brown adipose tissue, which burns fat. The drugs also stimulate the growth of new blood vessels in fat tissue, which positively reinforces the nanoparticle targeting and aids in the white-to-brown transformation. These drugs, which are not FDA-approved to treat obesity, are not new, but the research team developed a new way to deliver them so that they accumulate in fatty tissues, helping to avoid unwanted side effects in other parts of the body.

adiposetissue

The advantage here is now you have a way of targeting it to a particular area and not giving the body systemic effects. You can get the positive effects that you’d want in terms of antiobesity but not the negative ones that sometimes occur,” says Robert Langer, the David H. Koch Institute Professor at MIT and a member of MIT’s Koch Institute for Integrative Cancer Research.

More than one-third of Americans are considered to be obese, and last year obesity overtook smoking as the top preventable cause of cancer death in the United States, with 20 percent of the 600,000 cancer deaths attributed to obesity.

Langer and Omid Farokhzad, director of the Laboratory of Nanomedicine and Biomaterials at Brigham and Women’s Hospital, are the senior authors of the study, which appears in theProceedings of the National Academy of Sciences the week of May 2. The paper’s lead authors are former MIT postdoc Yuan Xue and former BWH postdoc Xiaoyang Xu.

Source: http://news.mit.edu/

Nanotechnology Improves Next Generation Of Batteries

In the global race to create more efficient and long-lasting batteries, some are betting on nanotechnology — the use of minuscule parts — as the most likely to yield a breakthrough. Improving batteries’ performance is key to the development and success of many much-hyped technologies, from solar and wind energy to electric cars. They need to hold more energy, last longer, be cheaper and safer. Research into how to achieve that has followed several avenues, from using different materials than the existing lithium-ion batteries to changing the internal structure of batteries using nanoparticles — parts so small they are invisible to the naked eye. Nanotechnology can increase the size and surface of batteries electrodes, the rods inside the batteries that absorb the energy. It does so by effectively making the electrodes sponge-like, so that they can absorb more energy during charging and ultimately increasing the energy storage capacity. Prague-based company HE3DA in Czech Republic has developed such a technology by using the nanotechnology to move from the current flat electrodes to make them three dimensional. With prototypes undergoing successful testing, it hopes to have the battery on the market at the end of this year.

Tesla Model 3

In the future, this will be the mainstream,” said Jan Prochazka, the president. He said it would be targeted at high-intensity industries like automobiles and the energy sector, rather than mobile phones, because that is where it can make the biggest difference through its use of his bigger electrodes.

In combination with an internal cooling system the batteries, which are being tested now, should be safe from overheating or exploding, a major concern with existing technologies. Researchers at the University of Michigan and MIT have likewise focused on nanotechnology to improve the existing lithium-ion technology. Others have sought to use different materials. One of the most promising is lithium oxygen, which theoretically could store five to 10 times the energy of a lithium ion battery, but there have been a number of technical problems that made it inefficient. Batteries based on sodium-ion, aluminium-air and aluminium-graphite are also being explored. There’s even research on a battery powered by urine.

Source: http://www.he3da.cz/
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