MIT: Researchers clarify mystery about proposed battery material – More “Energy Per Pound”- EV’s and Lithium-Air Batteries


MIT-Lithium-i-1_0Study explains conflicting results from other experiments, may lead to batteries with more energy per pound.

Battery researchers agree that one of the most promising possibilities for future battery technology is the lithium-air (or lithium-oxygen) battery, which could provide three times as much power for a given weight as today’s leading technology, lithium-ion batteries. But tests of various approaches to creating such batteries have produced conflicting and confusing results, as well as controversies over how to explain them.

Now, a team at MIT has carried out detailed tests that seem to resolve the questions surrounding one promising material for such batteries: a compound called lithium iodide (LiI). The compound was seen as a possible solution to some of the lithium-air battery’s problems, including an inability to sustain many charging-discharging cycles, but conflicting findings had raised questions about the material’s usefulness for this task. The new study explains these discrepancies, and although it suggests that the material might not be suitable after all, the work provides guidance for efforts to overcome LiI’s drawbacks or find alternative materials.battery-5001

The new results appear in the journal Energy and Environmental Science, in a paper by Yang Shao-Horn, MIT’s W.M. Keck Professor of Energy; Paula Hammond, the David H. Koch Professor in Engineering and head of the Department of Chemical Engineering; Michal Tulodziecki, a recent MIT postdoc at the Research Laboratory of Electronics; Graham Leverick, an MIT graduate student; Yu Katayama, a visiting student; and three others.

The promise of the lithium-air battery comes from the fact one of the two electrodes, which are usually made of metal or metal oxides, is replaced with air that flows in and out of the battery; a weightless substance is thus substituted for one of the heavy components. The other electrode in such batteries would be pure metallic lithium, a lightweight element.

But that theoretical promise has been limited in practice because of three issues: the need for high voltages for charging, a low efficiency with regard to getting back the amount of energy put in, and low cycle lifetimes, which result from instability in the battery’s oxygen electrode. Researchers have proposed adding lithium iodide in the electrolyte as a way of addressing these problems. But published results have been contradictory, with some studies finding the LiI does improve the cycling life, “while others show that the presence of LiI leads to irreversible reactions and poor battery cycling,” Shao-Horn says.

Previously, “most of the research was focused on organics” to make lithium-air batteries feasible, says Michal Tulodziecki, the paper’s lead author. But most of these organic compounds are not stable, he says, “and that’s why there’s been a great focus on lithium iodide [an inorganic material], which some papers said helps the batteries achieve thousands of cycles. But others say no, it will damage the battery.” In this new study, he says, “we explored in detail how lithium iodide affects the process, with and without water,” a comparison which turned out to be significant.

lithium-air-battery (1)

The team looked at the role of LiI on lithium-air battery discharge, using a different approach from most other studies. One set of studies was conducted with the components outside of the battery, which allowed the researchers to zero in on one part of the reaction, while the other study was done in the battery, to help explain the overall process.

They then used ultraviolet and visible-light spectroscopy and other techniques to study the reactions that took place. Both of these processes foster the production of different lithium compound such as LiOH (lithium hydroxide) in the presence of both LiI and water, instead of Li2O(lithium peroxide).  LiI can enhance water’s reactivity and make it lose protons more easily, which promotes the formation of LiOH in these batteries and interferes with the charging process. These observations show that finding ways to suppress these reactions could make compounds such as LiI work better.

This study could point the way toward selecting a different compound instead of LiI to perform its intended function of suppressing unwanted chemical reactions at the electrode surface, Leverick says, adding that this work demonstrates the importance of “looking at the detailed mechanism carefully.”

Shao-Horn says that the new findings “help get to the bottom of this existing controversy on the role of LiI on discharge. We believe this clarifies and brings together all these different points of view.”

But this work is just one step in a long process of trying to make lithium-air technology practical, the researchers say. “There’s so much to understand,” says Leverick, “so there’s not one paper that’s going to solve it. But we will make consistent progress.”

“Lithium-oxygen batteries that run on oxygen and lithium ions are of great interest because they could enable electric vehicles of much greater range. However, one of the problems is that they are not very efficient yet,” says Larry Curtiss, a distinguished fellow at Argonne National Laboratory, who was not involved in this work. In this study, he says, “it is shown how adding a simple salt, lithium iodide, can potentially be used to make these batteries run much more efficiently. They have provided new insight into how the lithium iodide acts to help break up the solid discharge product, which will help to enable the development of these advanced battery systems.”Nissan-Leaf

Curtiss adds that “there are still significant barriers remaining to be overcome before these batteries become a reality, such as getting long enough cycle life, but this is an important contribution to the field.”

The team also included recent MIT graduates Chibueze Amanchukwu PhD ’17 and David Kwabi PhD ’16, and Fanny Bardé of Toyota Motor Europe. The work was supported by Toyota Motor Europe and the Skoltech Center for Electrochemical Energy Storage, and used facilities supported by the National Science Foundation.

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MIT team creates flexible, transparent solar cells with graphene electrodes



Researchers at the Massachusetts Institute of Technology (MIT) have developed flexible and transparent graphene-based solar cells, which can be mounted on various surfaces ranging from glass to plastic to paper and tape. The graphene devices exhibited optical transmittance of 61% across the whole visible regime and up to 69% at 550 nanometers. The power conversion efficiency of the graphene solar cells ranged from 2.8% to 4.1%.

MIT team’s flexible, transparent solar cell with graphene electrodes image

A common challenge in making transparent solar cells with graphene is getting the two electrodes to stick together and to the substrate, as well as ensuring that electrons only flow out of one of the graphene layers. Using heat or glue can damage the material and reduce its conductivity, so the MIT team developed a new technique to tackle this issue. Rather than applying an adhesive between the graphene and the substrate, they sprayed a thin layer of ethylene-vinyl acetate (EVA) over the top, sticking them together like tape instead of glue.

The MIT team compared their graphene electrode solar cells against others made from standard materials like aluminum and indium tin oxide (ITO), built on rigid glass and flexible substrates. The power conversion efficiency (PCE) of the graphene solar cells was far lower than regular solar panels, but much better than previous transparent solar cells. This is a positive advancement, obviously.
Samples of solar cells using electrodes of different materials for testing image


Efficiency is often a trade-off from the graphene solar cells being flexible and transparent. In that regard the cells performed well, transmitting almost 70% of the light in the middle of the human range of vision. Hopefully the numbers will continue to improve. According to the researchers’ calculations, the efficiency of these graphene solar cells could be pushed as high as 10% without losing any transparency, and doing just that is the next step in the project. The researchers are also working on ways to scale up the system to cover windows and walls.
Source:  newatlas

Converging on Cancer at the Nanoscale


MIT-KI-Marble-Center-Faculty-00_0The Marble Center for Cancer Nanomedicine’s faculty is made up of Koch Institute members who are committed to fighting cancer with nanomedicine through research, education, and collaboration. Top row (l-r) Sangeeta Bhatia, director; Daniel Anderson; and Angela Belcher. Bottom row: Paula Hammond; Darrell Irvine; and Robert Langer. Photo: Koch Institute Marble Center for Cancer Nanomedicine

 Koch Institute – July 2017

Marking its first anniversary, the Koch Institute’s Marble Center for Cancer Nanomedicine goes full steam ahead.

This summer, the Koch Institute for Integrative Cancer Research at MIT marks the first anniversary of the launch of the Marble Center for Cancer Nanomedicine, established through a generous gift from Kathy and Curt Marble ’63.

Bringing together leading Koch Institute faculty members and their teams, the Marble Center for Cancer Nanomedicine focuses on grand challenges in cancer detection, treatment, and monitoring that can benefit from the emerging biology and physics of the nanoscale.

These challenges include detecting cancer earlier than existing methods allow, harnessing the immune system to fight cancer even as it evolves, using therapeutic insights from cancer biology to design therapies for previously undruggable targets, combining existing drugs for synergistic action, and creating tools for more accurate diagnosis and better surgical intervention. cancer-shapeshiftin

Koch Institute member Sangeeta N. Bhatia, the John J. and Dorothy Wilson Professor of Health Sciences and Technology and Electrical Engineering and Computer Science, serves as the inaugural director for the center.

”A major goal for research at the Marble Center is to leverage the collaborative culture at the Koch Institute to use nanotechnology to improve cancer diagnosis and care in patients around the world,” Bhatia says.

Transforming nanomedicine

The Marble Center joins MIT’s broader efforts at the forefront of discovery and innovation to solve the urgent global challenge that is cancer. The concept of “convergence” — the blending of the life and physical sciences with engineering — is a hallmark of MIT, the founding principle of the Koch Institute, and at the heart of the Marble Center’s mission.

“The center galvanizes the MIT cancer research community in efforts to use nanomedicine as a translational platform for cancer care,” says Tyler Jacks, director of the Koch Institute and a David H. Koch Professor of Biology. “It’s transformative by applying these emerging technologies to push the boundaries of cancer detection, treatment, and monitoring — and translational by promoting their development and application in the clinic.”

The center’s faculty — six prominent MIT professors and Koch Institute members — are committed to fighting cancer with nanomedicine through research, education, and collaboration. They are:

Sangeeta Bhatia (director), the John J. and Dorothy Wilson Professor of Health Sciences and Technology and Electrical Engineering and Computer Science;

Daniel G. Anderson, the Samuel A. Goldblith Professor of Applied Biology in the Department of Chemical Engineering and the Institute for Medical Engineering and Science;

Angela M. Belcher, the James Mason Crafts Professor in the departments of Biological Engineering and Materials Science and Engineering;

Paula T. Hammond, the David H. Koch Professor of Engineering and head of the Department of Chemical Engineering;

Darrell J. Irvine, professor in the departments of Biological Engineering and Materials Science and Engineering; and

Robert S. Langer, the David H. Koch Institute Professor.

Extending their collaboration within the walls of the Institute, Marble Center members benefit greatly from the support of the Peterson (1957) Nanotechnology Materials Core Facility in the Koch Institute’s Robert A. Swanson (1969) Biotechnology Center. The Peterson Facility’s array of technological resources and expertise is unmatched in the United States, and gives members of the center, and of the Koch Institute, a distinct advantage in the development and application of nanoscale materials and technologies.

Looking ahead

Figure-1-11-Nanocarriers-for-cancer-theranostics-Nanoparticles-based-strategies-can-beThe Marble Center has wasted no time getting up to speed in its first year, and has provided support for innovative research projects including theranostic nanoparticles that can both detect and treat cancers, real-time imaging of interactions between cancer and immune cells to better understand response to cancer immunotherapies, and delivery technologies for several powerful RNA-based therapeutics able to engage specific cancer targets with precision.

As part of its efforts to help foster a multifaceted science and engineering research force, the center has provided fellowship support for trainees — as well as valuable opportunities for mentorship, scientific exchange, and professional development.

Promoting broader engagement, the Marble Center serves as a bridge to a wide network of nanomedicine resources, connecting its members to MIT.nano, other nanotechnology researchers, and clinical collaborators across Boston and beyond. The center has also convened a scientific advisory board, whose members hail from leading academic and clinical centers around the country, and will help shape the center’s future programs and continued expansion.

As the Marble Center begins another year of collaborations and innovation, there is a new milestone in sight for 2018. Nanomedicine has been selected as the central theme for the Koch Institute’s 17th Annual Cancer Research Symposium. Scheduled for June 15, 2018, the event will bring together national leaders in the field, providing an ideal forum for Marble Center members to share the discoveries and advancements made during its sophomore year.

“Having next year’s KI Annual Symposium dedicated to nanomedicine will be a wonderful way to further expose the cancer research community to the power of doing science at the nanoscale,” Bhatia says. “The interdisciplinary approach has the power to accelerate new ideas at this exciting interface of nanotechnology and medicine.”

To learn more about the people and projects of the Koch Institute Marble Center for Cancer Nanomedicine, visit nanomedicine.mit.edu.

MIT: Antibiotic Nanoparticles Fight Drug-Resistant Bacteria


MIT-Nano-Anti_0Researchers are hoping to use nanotechnology to develop more targeted treatments for drug-resistant bacteria. In this illustration, an antimicrobial peptide is packaged in a silicon nanoparticle to target bacteria in the lung. Image: Jose-Luis Olivares/MIT

Targeted treatment could be used for pneumonia and other bacterial infections.

Antibiotic resistance is a growing problem, especially among a type of bacteria that are classified as “Gram-negative.” These bacteria have two cell membranes, making it more difficult for drugs to penetrate and kill the cells.

Researchers from MIT and other institutions are hoping to use nanotechnology to develop more targeted treatments for these drug-resistant bugs. In a new study, they report that an antimicrobial peptide packaged in a silicon nanoparticle dramatically reduced the number of bacteria in the lungs of mice infected with Pseudomonas aeruginosa, a disease causing Gram-negative bacterium that can lead to pneumonia.

This approach, which could also be adapted to target other difficult-to-treat bacterial infections such as tuberculosis, is modeled on a strategy that the researchers have previously used to deliver targeted cancer drugs.

“There are a lot of similarities in the delivery challenges. In infection, as in cancer, the name of the game is selectively killing something, using a drug that has potential side effects,” says Sangeeta Bhatia, the John and Dorothy Wilson Professor of Health Sciences and Technology and Electrical Engineering and Computer Science and a member of MIT’s Koch Institute for Integrative Cancer Research and Institute for Medical Engineering and Science.

Bhatia is the senior author of the study, which appears in the journal Advanced Materials. The lead author is Ester Kwon, a research scientist at the Koch Institute. Other authors are Matthew Skalak, an MIT graduate and former Koch Institute research technician; Alessandro Bertucci, a Marie Curie Postdoctoral Fellow at the University of California at San Diego; Gary Braun, a postdoc at the Sanford Burnham Prebys Medical Discovery Institute; Francesco Ricci, an associate professor at the University of Rome Tor Vergata; Erkki Ruoslahti, a professor at the Sanford Burnham Prebys Medical Discovery Institute; and Michael Sailor, a professor at UCSD.

Synergistic peptides

As bacteria grow increasingly resistant to traditional antibiotics, one alternative that some researchers are exploring is antimicrobial peptides — naturally occurring defensive proteins that can kill many types of bacteria by disrupting cellular targets such as membranes and proteins or cellular processes such as protein synthesis.

A few years ago, Bhatia and her colleagues began investigating the possibility of delivering antimicrobial peptides in a targeted fashion using nanoparticles. They also decided to try combining an antimicrobial peptide with another peptide that would help the drug cross bacterial membranes. This concept was built on previous work suggesting that these “tandem peptides” could kill cancer cells effectively.

For the antimicrobial peptide, the researchers chose a synthetic bacterial toxin called KLAKAK. They attached this toxin to a variety of “trafficking peptides,” which interact with bacterial membranes. Of 25 tandem peptides tested, the best one turned out to be a combination of KLAKAK and a peptide called lactoferrin, which was 30 times more effective at killing Pseudomonas aeruginosa than the individual peptides were on their own. It also had minimal toxic effects on human cells.

To further minimize potential side effects, the researchers packaged the peptides into silicon nanoparticles, which prevent the peptides from being released too soon and damaging tissue while en route to their targets. For this study, the researchers delivered the particles directly into the trachea, but for human use, they plan to design a version that could be inhaled.

After the nanoparticles were delivered to mice with an aggressive bacterial infection, those mice had about one-millionth the number of bacteria in their lungs as untreated mice, and they survived longer. The researchers also found that the peptides could kill strains of drug-resistant Pseudomonas taken from patients and grown in the lab.

Adapting concepts

Infectious disease is a fairly new area of research for Bhatia’s lab, which has spent most of the past 17 years developing nanomaterials to treat cancer. A few years ago, she began working on a project funded by the Defense Advanced Research Projects Agency (DARPA) to develop targeted treatments for infections of the brain, which led to the new lung infection project.

“We’ve adapted a lot of the same concepts from our cancer work, including boosting local concentration of the cargo and then making the cargo selectively interact with the target, which is now bacteria instead of a tumor,” Bhatia says.

She is now working on incorporating another peptide that would help to target antimicrobial peptides to the correct location in the body. A related project involves using trafficking peptides to help existing antibiotics that kill Gram-positive bacteria to cross the double membrane of Gram-negative bacteria, enabling them to kill those bacteria as well.

The research was funded by the Koch Institute Support Grant from the National Cancer Institute, the National Institute of Environmental Health Sciences, and DARPA.

Anne Trafton | MIT News Office

MIT Researchers develop new (low energy) way to Clear Pollutants from Water: w/ Video


MIT-PurifyingWater-1_0Researchers have developed a new method for removing even extremely low levels of unwanted compounds from water. The new method relies on an electrochemical process to selectively remove organic contaminants such as pesticides, chemical waste products, and pharmaceuticals. Photo: Melanie Gonick/MIT

Electrochemical method can remove even tiny amounts of contamination.

When it comes to removing very dilute concentrations of pollutants from water, existing separation methods tend to be energy- and chemical-intensive. Now, a new method developed at MIT could provide a selective alternative for removing even extremely low levels of unwanted compounds.

The new approach is described in the journal Energy and Environmental Science, in a paper by MIT postdoc Xiao Su, Ralph Landau Professor of Chemical Engineering T. Alan Hatton, and five others at MIT and at the Technical University of Darmstadt in Germany.

The system uses a novel method, relying on an electrochemical process to selectively remove organic contaminants such as pesticides, chemical waste products, and pharmaceuticals, even when these are present in small yet dangerous concentrations. The approach also addresses key limitations of conventional electrochemical separation methods, such as acidity fluctuations and losses in performance that can happen as a result of competing surface reactions. Watch the Video:

Current systems for dealing with such dilute contaminants include membrane filtration, which is expensive and has limited effectiveness at low concentrations, and electrodialysis and capacitive deionization, which often require high voltages that tend to produce side reactions, Su says. These processes also are hampered by excess background salts.

In the new system, the water flows between chemically treated, or “functionalized,” surfaces that serve as positive and negative electrodes. These electrode surfaces are coated with what are known as Faradaic materials, which can undergo reactions to become positively or negatively charged. These active groups can be tuned to bind strongly with a specific type of pollutant molecule, as the team demonstrated using ibuprofen and various pesticides. The researchers found that this process can effectively remove such molecules even at parts-per-million concentrations.

Previous studies have usually focused on conductive electrodes, or functionalized plates on just one electrode, but these often reach high voltages that produce contaminating compounds. By using appropriately functionalized electrodes on both the positive and negative sides, in an asymmetric configuration, the researchers almost completely eliminated these side reactions. Also, these asymmetric systems allow for simultaneous selective removal of both positive and negative toxic ions at the same time, as the team demonstrated with the herbicides paraquat and quinchlorac.

The same selective process should also be applied to the recovery of high-value compounds in a chemical or pharmaceutical production plant, where they might otherwise be wasted, Su says. “The system could be used for environmental remediation, for toxic organic chemical removal, or in a chemical plant to recover value-added products, as they would all rely on the same principle to pull out the minority ion from a complex multi-ion system.”

The system is inherently highly selective, but in practice it would likely be designed with multiple stages to deal with a variety of compounds in sequence, depending on the exact application, Su says. “Such systems might ultimately be useful,” he sugggests, “for water purification systems for remote areas in the developing world, where pollution from pesticides, dyes, and other chemicals are often an issue in the water supply. The highly efficient, electrically operated system could run on power from solar panels in rural areas for example.”

Unlike membrane-based systems that require high pressures, and other electrochemical systems that operate at high voltages, the new system works at relatively benign low voltages and pressures, Hatton says. And, he points out, in contrast to conventional ion exchange systems where release of the captured compounds and regeneration of the adsorbents would require the addition of chemicals, “in our case you can just flip a switch” to achieve the same result by switching the polarity of the electrodes.

The research team has already racked up a series of honors for the ongoing development of water treatment technology, including grants from the J-WAFS Solutions and Massachusetts Clean Energy Catalyst competitions, and the researchers were the top winners last year’s MIT Water Innovation Prize. The researchers have applied for a patent on the new process. “We definitely want to implement this in the real world,” Hatton says. In the meantime, they are working on scaling up their prototype devices in the lab and improving the chemical robustness.

This technique “is highly significant, as it extends the capabilities of electrochemical systems from basically nonselective toward highly selective removal of key pollutants,” says Matthew Suss, an assistant professor of mechanical engineering at Technion Institute of Technology in Israel, who was not involved in this work. “As with many emerging water purification techniques, it must still must be tested under real-world conditions and for long periods to check durability. However, the prototype system achieved over 500 cycles, which is a highly promising result.”

These researchers “have systematically explored a variety of device configurations and a variety of contaminants,” says Kyle Smith, a professor of mechanical science and engineering at the University of Illinois, who also was not involved in this work. “In the process they have identified general design principles by which to achieve selective removal of contaminants. In this regard, I find Hatton and co-workers’ study to be very thorough and thoughtful. It provides a framework or paradigm for other researchers to emulate.” But, he adds, “A significant challenge that remains is the scale-up of these technologies.”

The team also included Kai-Jher Tan, Johannes Elbert, and Robert R. Taylor Professor of Chemistry Timothy Jamison at MIT; and Christian Ruttiger and Markus Gallei at the Technical University of Darmstadt. The work was supported by a seed grant from the Abdul Latif Jameel World Water and Food Security Lab (J-WAFS) at MIT.

MIT: Antibiotic Nanoparticles fight drug-resistant bacteria


MIT-Nano-Anti_0

Researchers are hoping to use nanotechnology to develop more targeted treatments for drug-resistant bacteria. In this illustration, an antimicrobial peptide is packaged in a silicon nanoparticle to target bacteria in the lung.Image:  Jose-Luis Olivares/MIT

Antibiotic Nanoparticles fight drug-resistant bacteria

Targeted treatment could be used for pneumonia and other bacterial infections.

Antibiotic resistance is a growing problem, especially among a type of bacteria that are classified as “Gram-negative.” These bacteria have two cell membranes, making it more difficult for drugs to penetrate and kill the cells.

Researchers from MIT and other institutions are hoping to use nanotechnology to develop more targeted treatments for these drug-resistant bugs. In a new study, they report that an antimicrobial peptide packaged in a silicon nanoparticle dramatically reduced the number of bacteria in the lungs of mice infected with Pseudomonas aeruginosa, a disease causing Gram-negative bacterium that can lead to pneumonia.

This approach, which could also be adapted to target other difficult-to-treat bacterial infections such as tuberculosis, is modeled on a strategy that the researchers have previously used to deliver targeted cancer drugs.

“There are a lot of similarities in the delivery challenges. In infection, as in cancer, the name of the game is selectively killing something, using a drug that has potential side effects,” says Sangeeta Bhatia, the John and Dorothy Wilson Professor of Health Sciences and Technology and Electrical Engineering and Computer Science and a member of MIT’s Koch Institute for Integrative Cancer Research and Institute for Medical Engineering and Science.

Bhatia is the senior author of the study, which appears in the journal Advanced Materials. The lead author is Ester Kwon, a research scientist at the Koch Institute. Other authors are Matthew Skalak, an MIT graduate and former Koch Institute research technician; Alessandro Bertucci, a Marie Curie Postdoctoral Fellow at the University of California at San Diego; Gary Braun, a postdoc at the Sanford Burnham Prebys Medical Discovery Institute; Francesco Ricci, an associate professor at the University of Rome Tor Vergata; Erkki Ruoslahti, a professor at the Sanford Burnham Prebys Medical Discovery Institute; and Michael Sailor, a professor at UCSD.

Synergistic peptides

As bacteria grow increasingly resistant to traditional antibiotics, one alternative that some researchers are exploring is antimicrobial peptides — naturally occurring defensive proteins that can kill many types of bacteria by disrupting cellular targets such as membranes and proteins or cellular processes such as protein synthesis.

A few years ago, Bhatia and her colleagues began investigating the possibility of delivering antimicrobial peptides in a targeted fashion using nanoparticles. They also decided to try combining an antimicrobial peptide with another peptide that would help the drug cross bacterial membranes. This concept was built on previous work suggesting that these “tandem peptides” could kill cancer cells effectively.

For the antimicrobial peptide, the researchers chose a synthetic bacterial toxin called KLAKAK. They attached this toxin to a variety of “trafficking peptides,” which interact with bacterial membranes. Of 25 tandem peptides tested, the best one turned out to be a combination of KLAKAK and a peptide called lactoferrin, which was 30 times more effective at killing Pseudomonas aeruginosa than the individual peptides were on their own. It also had minimal toxic effects on human cells.

To further minimize potential side effects, the researchers packaged the peptides into silicon nanoparticles, which prevent the peptides from being released too soon and damaging tissue while en route to their targets. For this study, the researchers delivered the particles directly into the trachea, but for human use, they plan to design a version that could be inhaled.

After the nanoparticles were delivered to mice with an aggressive bacterial infection, those mice had about one-millionth the number of bacteria in their lungs as untreated mice, and they survived longer. The researchers also found that the peptides could kill strains of drug-resistant Pseudomonas taken from patients and grown in the lab.

Adapting concepts

Infectious disease is a fairly new area of research for Bhatia’s lab, which has spent most of the past 17 years developing nanomaterials to treat cancer. A few years ago, she began working on a project funded by the Defense Advanced Research Projects Agency (DARPA) to develop targeted treatments for infections of the brain, which led to the new lung infection project.

“We’ve adapted a lot of the same concepts from our cancer work, including boosting local concentration of the cargo and then making the cargo selectively interact with the target, which is now bacteria instead of a tumor,” Bhatia says.

She is now working on incorporating another peptide that would help to target antimicrobial peptides to the correct location in the body. A related project involves using trafficking peptides to help existing antibiotics that kill Gram-positive bacteria to cross the double membrane of Gram-negative bacteria, enabling them to kill those bacteria as well.

The research was funded by the Koch Institute Support Grant from the National Cancer Institute, the National Institute of Environmental Health Sciences, and DARPA.

 

MIT: Dialysis membrane made from Graphene filters more quickly


MIT Dialysis 170629131958_1_540x360
1) Graphene, grown on copper foil, is pressed against a supporting sheet of polycarbonate. 2) The polycarbonate acts to peel the graphene from the copper. 3) Using interfacial polymerization, researchers seal large tears and defects in graphene. 4) Next, they use oxygen plasma to etch pores of specific sizes in graphene.
Credit: Courtesy of the researchers (edited by MIT News)

Material can filter nanometer-sized molecules at 10 to 100 times the rate of commercial membranes

Source: Massachusetts Institute of Technology

Summary: A functional dialysis membrane has been fabricated 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.

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 membranes 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.

MIT Dialysis 170629131958_1_540x360“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 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.

Plugging graphene

To make the graphene membrane, the researchers first used a common technique called chemical vapor deposition to grow graphene on copper foil. They then carefully etched away the copper and transferred the graphene to a supporting sheet of polycarbonate, studded throughout with pores large enough to let through any molecules that have passed through the graphene. The polycarbonate acts as a scaffold, keeping the ultrathin graphene from curling up on itself.

The researchers looked to turn graphene into a molecularly selective sieve, letting through only molecules of a certain size. To do so, they created tiny pores in the material by exposing the structure to oxygen plasma, a process by which oxygen, pumped into a plasma chamber, can etch away at materials.

“By tuning the oxygen plasma conditions, we can control the density and size of pores we make, in the areas where the graphene is pristine,” Kidambi says. “What happens is, an oxygen radical comes to a carbon atom [in graphene] and rapidly reacts, and they both fly out as carbon dioxide.”

What is left is a tiny hole in the graphene, where a carbon atom once sat. Kidambi and his colleagues found that the longer graphene is exposed to oxygen plasma, the larger and more dense the pores will be. Relatively short exposure times, of about 45 to 60 seconds, generate very small pores.

Desirable defects

The researchers tested multiple graphene membranes with pores of varying sizes and distributions, placing each membrane in the middle of a diffusion chamber. They filled the chamber’s feed side with a solution containing various mixtures of molecules of different sizes, ranging from potassium chloride (0.66 nanometers wide) to vitamin B12 (1 to 1.5 nanometers) and lysozyme (4 nanometers), a protein found in egg white. The other side of the chamber was filled with a dilute solution.

The team then measured the flow of molecules as they diffused through each graphene membrane.

Membranes with very small pores let through potassium chloride but not larger molecules such as L-tryptophan, which measures only 0.2 nanometers wider. Membranes with larger pores let through correspondingly larger molecules.

The team carried out similar experiments with commercial dialysis membranes and found that, in comparison, the graphene membranes performed with higher “permeance,” filtering out the desired molecules up to 10 times faster.

Kidambi points out that the polycarbonate support is etched with pores that only take up 10 percent of its surface area, which limits the amount of desired molecules that ultimately pass through both layers.

“Only 10 percent of the membrane’s area is accessible, but even with that 10 percent, we’re able to do better than state-of-the-art,” Kidambi says.

To make the graphene membrane even better, the team plans to improve the polycarbonate support by etching more pores into the material to increase the membrane’s overall permeance. They are also working to further scale up the dimensions of the membrane, which currently measures 1 square centimeter. Further tuning the oxygen plasma process to create tailored pores will also improve a membrane’s performance — something that Kidambi points out would have vastly different consequences for graphene in electronics applications.

“What’s exciting is, what’s not great for the electronics field is actually perfect in this [membrane dialysis] field,” Kidambi says. “In electronics, you want to minimize defects. Here you want to make defects of the right size. It goes to show the end use of the technology dictates what you want in the technology. That’s the key.”


Story Source:

Materials provided by Massachusetts Institute of Technology. Original written by Jennifer Chu. Note: Content may be edited for style and length.


Journal Reference:

  1. Piran R. Kidambi, Doojoon Jang, Juan-Carlos Idrobo, Michael S. H. Boutilier, Luda Wang, Jing Kong, Rohit Karnik. Nanoporous Atomically Thin Graphene Membranes for Desalting and Dialysis ApplicationsAdvanced Materials, 2017; 1700277 DOI: 10.1002/adma.201700277

MIT: A BIG step toward mass-producible quantum computers


Quantum Computer Big Step Mass P id46842

A team of researchers from MIT, Harvard University, and Sandia National Laboratories reports a new technique for creating targeted defects in diamond materials, which is simpler and more precise than its predecessors and could benefit diamond-based quantum computing devices.

Quantum computers are experimental devices that offer large speedups on some computational problems. One promising approach to building them involves harnessing nanometer-scale atomic defects in diamond materials.But practical, diamond-based quantum computing devices will require the ability to position those defects at precise locations in complex diamond structures, where the defects can function as qubits, the basic units of information in quantum computing. In Nature Communications (“Scalable focused ion beam creation of nearly lifetime-limited single quantum emitters in diamond nanostructures”), a team of researchers from MIT, Harvard University, and Sandia National Laboratories reports a new technique for creating targeted defects, which is simpler and more precise than its predecessors.

In experiments, the defects produced by the technique were, on average, within 50 nanometers of their ideal locations.
“The dream scenario in quantum information processing is to make an optical circuit to shuttle photonic qubits and then position a quantum memory wherever you need it,” says Dirk Englund, an associate professor of electrical engineering and computer science who led the MIT team. “We’re almost there with this. These emitters are almost perfect.”
The new paper has 15 co-authors. Seven are from MIT, including Englund and first author Tim Schröder, who was a postdoc in Englund’s lab when the work was done and is now an assistant professor at the University of Copenhagen’s Niels Bohr Institute. Edward Bielejec led the Sandia team, and physics professor Mikhail Lukin led the Harvard team.

Appealing defects

Quantum computers, which are still largely hypothetical, exploit the phenomenon of quantum “superposition,” or the counterintuitive ability of small particles to inhabit contradictory physical states at the same time. An electron, for instance, can be said to be in more than one location simultaneously, or to have both of two opposed magnetic orientations.
Where a bit in a conventional computer can represent zero or one, a “qubit,” or quantum bit, can represent zero, one, or both at the same time. It’s the ability of strings of qubits to, in some sense, simultaneously explore multiple solutions to a problem that promises computational speedups.
Diamond-defect qubits result from the combination of “vacancies,” which are locations in the diamond’s crystal lattice where there should be a carbon atom but there isn’t one, and “dopants,” which are atoms of materials other than carbon that have found their way into the lattice. Together, the dopant and the vacancy create a dopant-vacancy “center,” which has free electrons associated with it. The electrons’ magnetic orientation, or “spin,” which can be in superposition, constitutes the qubit.
A perennial problem in the design of quantum computers is how to read information out of qubits. Diamond defects present a simple solution, because they are natural light emitters. In fact, the light particles emitted by diamond defects can preserve the superposition of the qubits, so they could move quantum information between quantum computing devices.

Silicon switch

The most-studied diamond defect is the nitrogen-vacancy center, which can maintain superposition longer than any other candidate qubit. But it emits light in a relatively broad spectrum of frequencies, which can lead to inaccuracies in the measurements on which quantum computing relies.
In their new paper, the MIT, Harvard, and Sandia researchers instead use silicon-vacancy centers, which emit light in a very narrow band of frequencies. They don’t naturally maintain superposition as well, but theory suggests that cooling them down to temperatures in the millikelvin range — fractions of a degree above absolute zero — could solve that problem. (Nitrogen-vacancy-center qubits require cooling to a relatively balmy 4 kelvins.)
To be readable, however, the signals from light-emitting qubits have to be amplified, and it has to be possible to direct them and recombine them to perform computations. That’s why the ability to precisely locate defects is important: It’s easier to etch optical circuits into a diamond and then insert the defects in the right places than to create defects at random and then try to construct optical circuits around them.
In the process described in the new paper, the MIT and Harvard researchers first planed a synthetic diamond down until it was only 200 nanometers thick. Then they etched optical cavities into the diamond’s surface. These increase the brightness of the light emitted by the defects (while shortening the emission times).
Then they sent the diamond to the Sandia team, who have customized a commercial device called the Nano-Implanter to eject streams of silicon ions. The Sandia researchers fired 20 to 30 silicon ions into each of the optical cavities in the diamond and sent it back to Cambridge.

Mobile vacancies

At this point, only about 2 percent of the cavities had associated silicon-vacancy centers. But the MIT and Harvard researchers have also developed processes for blasting the diamond with beams of electrons to produce more vacancies, and then heating the diamond to about 1,000 degrees Celsius, which causes the vacancies to move around the crystal lattice so they can bond with silicon atoms.
After the researchers had subjected the diamond to these two processes, the yield had increased tenfold, to 20 percent. In principle, repetitions of the processes should increase the yield of silicon vacancy centers still further.
When the researchers analyzed the locations of the silicon-vacancy centers, they found that they were within about 50 nanometers of their optimal positions at the edge of the cavity. That translated to emitted light that was about 85 to 90 percent as bright as it could be, which is still very good.
Source: By Larry Hardesty, MIT

 

MIT: Advanced thin-film technique could deliver long-lasting medication: 1 in 4 Seniors could benefit


Paula Hammond MIT 1-implantable-film-MITMIT professor Paula Hammond (right) and Bryan Hsu PhD’ 14 have developed a nanoscale film that can be used to deliver medication, either directly through injections, or by coating implantable medical devices. Photo: Dominick Reuter

Nanoscale, biodegradable drug-delivery method could provide a year or more of steady doses.

About one in four older adults suffers from chronic pain. Many of those people take medication, usually as pills. But this is not an ideal way of treating pain: Patients must take medicine frequently, and can suffer side effects, since the contents of pills spread through the bloodstream to the whole body.

Now researchers at MIT have refined a technique that could enable pain medication and other drugs to be released directly to specific parts of the body — and in steady doses over a period of up to 14 months.  The method uses biodegradable, nanoscale “thin films” laden with drug molecules that are absorbed into the body in an incremental process.

“It’s been hard to develop something that releases [medication] for more than a couple of months,” says Paula Hammond, the David H. Koch Professor in Engineering at MIT, and a co-author of a new paper on the advance. “Now we’re looking at a way of creating an extremely thin film or coating that’s very dense with a drug, and yet releases at a constant rate for very long time periods.”

In the paper, published today in the Proceedings of the National Academy of Sciences, the researchers describe the method used in the new drug-delivery system, which significantly exceeds the release duration achieved by most commercial controlled-release biodegradable films.

“You can potentially implant it and release the drug for more than a year without having to go in and do anything about it,” says Bryan Hsu PhD ’14, who helped develop the project as a doctoral student in Hammond’s lab. “You don’t have to go recover it. Normally to get long-term drug release, you need a reservoir or device, something that can hold back the drug. And it’s typically nondegradable. It will release slowly, but it will either sit there and you have this foreign object retained in the body, or you have to go recover it.”

Layer by layer

The paper was co-authored by Hsu, Myoung-Hwan Park of Shamyook University in South Korea, Samantha Hagerman ’14, and Hammond, whose lab is in the Koch Institute for Integrative Cancer Research at MIT.

The research project tackles a difficult problem in localized drug delivery: Any biodegradable mechanism intended to release a drug over a long time period must be sturdy enough to limit hydrolysis, a process by which the body’s water breaks down the bonds in a drug molecule. If too much hydrolysis occurs too quickly, the drug will not remain intact for long periods in the body. Yet the drug-release mechanism needs to be designed such that a drug molecule does, in fact, decompose in steady increments.

To address this, the researchers developed what they call a “layer-by-layer” technique, in which drug molecules are effectively attached to layers of thin-film coating. In this specific case, the researchers used diclofenac, a nonsteroidal anti-inflammatory drug that is often prescribed for osteoarthritis and other pain or inflammatory conditions. They then bound it to thin layers of poly-L-glutamatic acid, which consists of an amino acid the body reabsorbs, and two other organic compounds. The film can be applied onto degradable nanoparticles for injection into local sites or used to coat permanent devices, such as orthopedic implants.

In tests, the research team found that the diclofenac was steadily released over 14 months. Because the effectiveness of pain medication is subjective, they evaluated the efficacy of the method by seeing how well the diclofenac blocked the activity of cyclooxygenase (COX), an enzyme central to inflammation in the body.

“We found that it remains active after being released,” Hsu says, meaning that the new method does not damage the efficacy of the drug. Or, as the paper notes, the layer-by-layer method produced “substantial COX inhibition at a similar level” to pills.

The method also allows the researchers to adjust the quantity of the drug being delivered, essentially by adding more layers of the ultrathin coating.

A viable strategy for many drugs

Hammond and Hsu note that the technique could be used for other kinds of medication; an illness such as tuberculosis, for instance, requires at least six months of drug therapy.

“It’s not only viable for diclofenac,” Hsu says. “This strategy can be applied to a number of drugs.”

Indeed, other researchers who have looked at the paper say the potential medical versatility of the thin-film technique is of considerable interest.

“I find it really intriguing because it’s broadly applicable to a lot of systems,” says Kathryn Uhrich, a professor in the Department of Chemistry and Chemical Biology at Rutgers University, adding that the research is “really a nice piece of work.”

To be sure, in each case, researchers will have to figure out how best to bind the drug molecule in question to a biodegradable thin-film coating. The next steps for the researchers include studies to optimize these properties in different bodily environments and more tests, perhaps with medications for both chronic pain and inflammation.

A major motivation for the work, Hammond notes, is “the whole idea that we might be able to design something using these kinds of approaches that could create an [easier] lifestyle” for people with chronic pain and inflammation.

Hsu and Hammond were involved in all aspects of the project and wrote the paper, while Hagerman and Park helped perform the research, and Park helped analyze the data.

The research described in the paper was supported by funding from the U.S. Army and the U.S. Air Force.

MIT: Using light to propel water ~ Significant  Applications in Oil Field Production



A new system developed by engineers at MIT could make it possible to control the way water moves over a surface, using only light. This advance may open the door to technologies such as microfluidic diagnostic devices whose channels and valves could be reprogrammed on the fly, or field systems that could separate water from oil at a drilling rig, the researchers say.

The system, reported in the journal Nature Communications (“Visible light guided manipulation of liquid wettability on photoresponsive surfaces”), was developed by MIT associate professor of mechanical engineering Kripa Varanasi, School of Engineering Professor of Teaching Innovation Gareth McKinley, former postdoc Gibum Kwon, graduate student Divya Panchanathan, former research scientist Seyed Mahmoudi, and Mohammed Gondal at the King Fahd University of Petroleum and Minerals in Saudi Arabia.

 

By creating surfaces whose interactions with water — a property known as wettability — can be activated by light, the researchers found they could directly separate oil from water. The process causes individual droplets of water to coalesce and spread across the surface. (Image courtesy of the researchers)

The initial goal of the project was to find ways of separating oil from water, for example, to treat the frothy mixture of briny water and crude oil produced from certain oil wells. The more thoroughly these mixtures are intermingled — the finer the droplets are — the harder they are to separate. Sometimes electrostatic methods are used, but these are energy-intensive and don’t work when the water is highly saline, as is often the case. Instead, the team explored the use of “photoresponsive” surfaces, whose responses to water can be altered by exposure to light.

By creating surfaces whose interactions with water — a property known as wettability — could be activated by light, the researchers found they could directly separate the oil from the water by causing individual droplets of water to coalesce and spread across the surface. The more the water droplets fuse together, the more they separate from the oil.

Photoresponsive materials have been widely studied and used; one example is the active ingredient in most sunscreens, titanium dioxide, also known as titania. But most of these materials, including titania, respond primarily to ultraviolet light and hardly at all to visible light. Yet only about 5 percent of sunlight is in the ultraviolet range. So the researchers figured out a way to treat the titania surface to make it responsive to visible light.

Driving droplets of water across a surface with light


The method also be used to drive droplets of water across a surface, as the team demonstrated in a series of experiments. By selectively changing the material’s wettability using a moving beam of light, a droplet can be directed toward the more wettable area, propelling it in any desired direction with great precision. (Image courtesy of the researchers)

They did so by first using a layer-by-layer deposition technique to build up a film of polymer-bound titania particles on a layer of glass. Then they dip-coated the material with a simple organic dye. The resulting surface turned out to be highly responsive to visible light, producing a change in wettability when exposed to sunlight that is much greater than that of the titania itself.
When activated by sunlight, the material proved very effective at “demulsifying” the oil-water mixture — getting the water and oil to separate from each other.

“We were inspired by the work in photovoltaics, where dye sensitization was used to improve the efficiency of absorption of solar radiation,” says Varansi. “The coupling of the dye to titania particles allows for the generation of charge carriers upon light illumination. This creates an electric potential difference to be established between the surface and the liquid upon illumination, and leads to a change in the wetting properties.”

“Saline water spreads out on our surface under illumination, but oil doesn’t,” says Kwon, who is now an assistant professor at the University of Kansas. “We found that virtually all the seawater will spread out on the surface and get separated from crude oil, under visible light.”

The same effect could also be used to drive droplets of water across a surface, as the team demonstrated in a series of experiments. By selectively changing the material’s wettability using a moving beam of light, a droplet can be directed toward the more wettable area, propelling it in any desired direction with great precision.
Such systems could be designed to make microfluidic devices without built-in boundaries or structures. The movement of liquid — for example a blood sample in a diagnostic lab-on-a-chip — would be entirely controlled by the pattern of illumination being projected onto it.


The photoresponsive effect can be highly tuned by selecting from among thousands of available organic dyes. (Image courtesy of the researchers)

“By systematically studying the relationship between the energy levels of the dye and the wettability of the contacting liquid, we have come up with a framework for the design of these light-guided liquid manipulation systems,” Varanasi says. “By choosing the right kind of dye, we can create a significant change in droplet dynamics. It’s light-induced motion – a touchless motion of droplets.”

The switchable wettability of these surfaces has another benefit: They can be largely self-cleaning. When the surface is switched from water-attracting (hydrophilic) to water-repelling (hydrophobic), any water on the surface gets driven off, carrying with it any contaminants that may have built up.

Since the photoresponsive effect is based on the dye coating, it can be highly tuned by selecting from among the thousands of available organic dyes. All of the materials involved in the process are widely available, inexpensive, commodity materials, the researchers say, and the processes for making them are commonplace.

Source: By David L. Chandler, MIT