$2 million NSF grant funds physicists' quest for optical transistors

"The ultimate goal is making it possible to devise all-optical computers and telecommunications," says Hayk Harutyunyan, left, with Ajit Srivastava. (Ann Borden, Emory Photo/Video)

By Carol Clark

The National Science Foundation awarded two Emory physicists a $2 million Emergent Frontiers grant, for development of miniaturized optical transistors to take computers and telecommunications into a new era.

“We are working to change some properties of light — such as making it travel in only one direction — by using atomically thin, two-dimensional materials,” says Ajit Srivastava, assistant professor of physics and principal investigator for the grant. “These novel materials are being touted as the next silicon. They could open the door to even smaller and more efficient electronics than are possible today.”

Srivastava’s co-investigators include Hayk Harutyunyan, also an assistant professor of physics at Emory, as well as scientists from Georgia State and Stanford universities.

“The ultimate goal is making it possible to devise all-optical computers and telecommunications,” Harutyunyan says.

A major revolution in telecommunications occurred in the 1950s, driven by the development of silicon semiconductors as miniature transistors to control the flow of electrical current. These transistors led to smaller, faster computers and paved the way for everything from flatscreen TVs to cell phones.

“They changed civilization,” Harutyunyan says. “Every year new computers would come out with faster processors as the transistors got tinier and more efficient. But about a decade ago this progress stopped, because these transistors cannot be made any smaller than about 15 nanometers and still function well.”

Meanwhile, the gradual replacement of copper wiring with fiber optics is speeding up transmissions between computers and other electronic devices and allowing for greater bandwidth. “When you send an email from Atlanta to Europe, the information is encoded into light and relayed by fiber optic cables running under the ocean,” Srivastava explains. “It’s super fast, because light is the fastest thing that you can imagine.”

Unlike in our everyday life, however, where the arrow of time moves in one direction, light photons operate at the quantum scale and can move back and forth. This lack of a fixed direction is called reciprocity. “Reciprocity in optics,” Srivastava says, “can best be described by a familiar observation: ‘If I can see you, you can see me.’”

Fiber optic cables use magnetic fields to break reciprocity and prevent light from reflecting off surfaces and creating “noise” in a signal. The required magnetic devices, known as optical isolators, are typically bulky and heavy because tiny magnets are not strong enough to do the job.

The Emory project aims to develop powerful nonreciprocal optical devices that are not based on magnets and can function at the nanoscale.

Srivastava’s lab is investigating the potential of transition metal dichalcogenides, or TMDs. TMDs are semiconductors within a new family of two-dimensional, extraordinarily thin materials. While the smallest feature of a current computer processor is 14 nanometers thick, a TMD monolayer is smaller than a single nanometer.

Harutyunyan’s lab, meanwhile, is exploring ways to make interactions between light and matter stronger through the use of metallic nano particles. Metals are shiny because of their free electrons that easily interact with light. The oscillations of these free electrons, called plasmons, allow metallic nano-particles to funnel large amounts of light into tiny dimensions.

A long-term goal of the project is to hybridize TMDs and metallic particles into nanomaterials that use laser fields to create the same light-guiding effects of magnetic fields. Such devices have the potential to be faster and cheaper and offer more precise control of the light-directing process. They would also be much smaller than existing optical isolators and transistors.

“Nano-science is an exciting area,” Srivastava says. “You can imagine the possibility of flexible cell phones or even wearable electronic membranes that would take the shape of your body.”

More powerful computers could also ramp up the ability of scientists to analyze massive datasets faster, Harutyunyan notes.

The Emory grant will also fund public outreach projects in Atlanta area schools. “We want people to understand the importance of fundamental science research,” Harutyunyan says. “And we want to inspire young people to think about science careers.

CDC funds Emory project to automate analysis of mixed strains of antibiotic-resistant bacteria

An electron micrograph shows human immune system cells attacking methicillin-resistant Staphylococcus aureus (MRSA). MRSA is an example of antibiotic-resistant bacteria that can occur in multiple strains in an infection, further complicating diagnosis, treatment and interventions.

By Carol Clark

The Centers for Disease Control and Prevention (CDC) awarded $380,000 to three Emory University faculty to develop and refine a promising technique to detect and respond to threats from drug-resistant pathogens.

The grant investigators include Lars Ruthotto and Ymir Vigfusson — both assistant professors in the Department of Mathematics and Computer Science — and Rebecca Mitchell, a visiting professor with a joint appointment in the Department of Mathematics and Computer Science and the Nell Hodgson Woodruff School of Nursing. 

The trio is developing a method to quickly and cost-effectively diagnose multiple strains of antibiotic-resistant bacteria within a single biological sample.

“This project harmonizes our different scientific specialties,” Vigfusson says. He is a computer scientist who develops software and programming algorithms that work at scale, while Ruthotto is a mathematician who focuses on solving inverse problems. Mitchell is a veterinarian and epidemiologist experienced in gathering biological samples and testing them for pathogens. 

Antibiotic-resistant infections are a growing national and global problem, causing at least two million illnesses and 23,000 deaths in the United States annually, according to the CDC.

The Emory grant is part of a $9 million package of CDC funding announced today, including awards to projects at 25 leading research institutions around the country that are exploring gaps in knowledge about antibiotic resistance and piloting innovative solutions in the healthcare, veterinary and agriculture industries. The work complements broader CDC efforts to support known strategies for protecting people and slowing antibiotic resistance, collectively known as the CDC Antibiotic Resistance Solutions Initiative.

The Emory project seeks to tame the complexity of analyzing multiple infections within a biological specimen, from a drop of blood to a fecal sample. In the case of a widespread outbreak of antibiotic-resistant E. coli for instance, it would be useful to quickly determine whether fecal samples contained multiple strains of the bacteria and what those strains were, in order to more rapidly trace the sources of the outbreak and design effective interventions.

It is costly and labor-intensive, however, to culture biological samples at the local level, and then send them to the CDC for testing. And if multiple strains of a pathogen are within a single sample, only some strains that are present may grow in the culture while other strains may be missed.

“It’s a challenge to deal with samples containing mixed strains of a pathogen in a lab setting,” Mitchell says. “You have to do a large amount of work to get the finer gradations of what species of pathogens are present, and in what proportions.”

The Emory researchers are striving to balance accuracy with the need to simplify and streamline the process. Their method eliminates labor-intensive, technical steps, such as culturing the sample. “We want to automate the process so that you need less expertise at the local level, and so that data coming from individual states can be easily integrated into a central system,” Mitchell explains.

They use multiple short polymorphic regions in the genome to look for genetic variations among the DNA templates present within a biological sample. In the case of antibiotic-resistant bacteria, the number of reference sites ranges between the hundreds to the thousands, depending on the specific bacteria targeted.

“We’ve developed an algorithm and software and mathematical models to rapidly run these comparisons and estimate the number of strains in a single sample, and the percentage of each,” Ruthotto says. “Now we are trying to quantify the accuracy of this estimate, which is a mathematical challenge. The grant gives us the resources to refine our method for real-world applications.”

The ultimate goal is to develop a system that will work not just on antibiotic-resistant bacteria, but for mixed-strains of any pathogen within a biological sample. In a separate project, for example, Mitchell and Vigfusson are applying the method to test for multiple strains of the malaria parasite within a blood sample.

“Quickly teasing apart mixed-strain samples is a big challenge in public health, and it’s essential in order to plan effective interventions,” Mitchell says.

“We’re using math and computer science to draw more information from a single biological sample than was previously practical,” Vigfusson says. “We hope that our method could turn into a work engine that helps to understand multiple-strain infections and makes an impact on public health.”

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Responding to climate change

By Martha McKenzie
Emory Public Health

Climate change. Partisan politicians debate its reality, and many citizens see it as a faraway threat, something that endangers the future of polar bears but not them personally.

The health effects of global warming, however, are already being felt. Extreme weather events such as wildfires, droughts, and flooding are becoming more frequent, resulting in more injuries, deaths, and relocations. Heat and air pollution are sending people with asthma and other respiratory ailments to the emergency room. Diseases carried by mosquitoes, fleas, and ticks are expanding their territory—dengue has become endemic in Florida, Lyme disease has worked its way up to Canada and over to California, and some fear that malaria may re-emerge in the U.S.

Tie these health burdens—which are only likely to worsen—with the current administration’s decision to pull out of the Paris climate agreement and dismantle environmental regulations, and the call to action becomes more urgent. “The federal government’s actions might be a headwind from a funding perspective, but they are also very much a tailwind from an inspiration and motivation perspective,” says Daniel Rochberg, an instructor in environmental health who worked for the U.S. State Department as special assistant to the lead U.S. climate negotiators under presidents Bush and Obama. “As others have said, ‘We are the first generation to feel the sting of climate change, and we are the last generation that can do something about it.’ We have to get busy doing something about it.”

Rollins School of Public Health has gotten busy. Faculty researchers are building the science of climate impacts, strategies for reducing greenhouse gas emissions, and approaches for increasing resilience to climate change. Climate@Emory, a university-wide organization of concerned students, faculty, and staff, is partnering with other academic institutions, industries, and governments to support education and climate remediation efforts. Through Climate@Emory’s initiative, Emory University is an accredited, official observer to the UN climate talks and has sent students and faculty to the climate conferences in Paris in 2015 and in Marrakech in 2016. And, of course, Rollins is educating the next generation of scientists who will be dealing with the fallout of today’s climate decisions.

“For environmental scientists, it’s a challenging climate,” says Paige Tolbert, O. Wayne Rollins Chair of Environmental Health. “That means we have to be creative, because we can’t step aside and wait four years. It’s more critical than ever that we keep moving forward and make whatever contributions we possibly can.”

Read more in Emory Public Health.

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NSF awards Emory's Center for Selective C-H Functionalization $20 million

"We’ve developed advanced catalysts that allow us to control which carbon-hydrogen bond within a molecule will react and when," says Huw Davies, director of the Center for Selective C-H Functionalization. (Graphic/photo by Stephen Nowland and Dan Morton)

By Carol Clark

The National Science Foundation has awarded another $20 million to Emory University’s Center for Selective C-H Functionalization, to fund the next phase of a global effort to revolutionize the field of organic synthesis.

“Our center is at the forefront of a major shift in the way that we do chemistry,” says Huw Davies, professor of chemistry at Emory and the director of the Center for Selective C-H Functionalization (CCHF). “This shift holds great promise for creating new pathways for drug discovery and the production of new materials to benefit everything from agriculture to electronics.”

The CCHF began as an NSF Center for Chemical Innovation in 2009, with a seed grant of $1.5 million and four collaborating universities. In 2012, the NSF awarded the CCHF its first $20 million, enabling it to grow to encompass 16 U.S. institutions and seven industrial affiliates, including six major pharmaceutical companies and one of the largest U.S. chemical suppliers. The center also built global connections with major players in C-H functionalization in Japan, South Korea and the U.K. 

The CCHF has led the way for explosive growth in the field of C-H functionalization, publishing more than 200 papers on the topic through its collaborators. It has developed dozens of new catalysts for C-H functionalization, including four major classes from the Huw Davies group.

“The past five years we’ve developed the fundamentals for C-H functionalization and documented that the concept is viable,” Davies says. “Now we’re ideally positioned to maximize the further development of this chemistry and move forward to apply it.”

Huw Davies, right, in his lab with Emory post-doctoral fellow Sidney Wilkerson-Hill, left, and Emory junior Patricia Chi Lin. The CCHF has developed dozens of new catalysts for C-H functionalization, including four major classes from the Davies group. (Photo by Stephen Nowland, Emory Photo Video)

Traditionally, organic chemistry has focused on the division between reactive, or functional, molecular bonds and the inert, or non-functional bonds carbon-carbon (C-C) and carbon-hydrogen (C-H). The inert bonds provide a strong, stable scaffold for performing chemical synthesis with the reactive groups. C-H functionalization flips this model on its head. 

“We’ve devised ways to make C-H bonds react so that they become functional,” Davies says. “And we’ve reached the stage where it is no longer the molecule itself that determines the process of the reaction — we’ve developed advanced catalysts that allow us to control which carbon-hydrogen bond within a molecule will react and when.”

C-H functionalization opens unexplored chemical space by taking petroleum byproducts, which have a lot of carbon-hydrogen bonds, and transforming them from waste into useful materials. It also strips out steps from the linear process of traditional organic synthesis, making it faster and more efficient.

The CCHF is not only transforming organic synthesis — it’s also creating new models for the way that organic chemistry is taught and that labs conduct research. Where previously individual labs tended to work in isolation to tackle problems, the CCHF has broken down walls across specialties, institutions and even countries to collectively take on the remaining challenges of selective C-H functionalization.

“We’ve got this incredible collaborative environment where organic chemists aren’t just sharing results — they’re sharing ideas,” Davies says. “That’s rare. And we’ve expanded that environment beyond our network of universities to also engage the pharmaceutical industry.”

In 2015, the CCHF launched an online symposia on recent advances in C-H functionalization. More than 1,000 graduate students and chemistry faculty from up to 45 countries join the symposia, held about four times a year, via the Internet.

“We have leading voices in the field give these free talks that are easy to join live and participate in,” Davies says. “The aim is to further expand the field of C-H functionalization by introducing it to graduate students and other chemists around the world.”

Related:
Chemists find 'huge shortcut' for organic synthesis using C-H bonds
NSF chemistry center opens new era in organic synthesis