Spot News Roundup

Medical Imaging Innovator Christine Hendon Wins Presidential Honor
Christine Hendon, an electrical engineer who develops innovative medical imaging instruments for use in surgery and breast cancer detection without the use of radiation, has won the Presidential Early Career Award for Scientists and Engineers (PECASE), the highest honor the U.S. government gives to young scientists and engineers. She was one of 102 researchers honored this year.

“These innovators are working to help keep the United States on the cutting edge, showing that federal investments in science lead to advancements that expand our knowledge of the world around us and contribute to our economy,” President Obama said in bestowing the awards in early January.

Hendon develops optical tools that aim to provide surgeons with a clear understanding of the tissue on which they are operating. She uses near-infrared spectroscopy and optical coherence tomography (OCT), a noninvasive imaging technique nicknamed “optical ultrasound” that provides depth-resolved, high-resolution images of tissue microstructure in real time. These “optical biopsies” offer much higher resolution than current medical imaging options. Using OCT, a surgeon could image a wide area of tissue and, unlike invasive biopsies, remove as little tissue as possible. Hendon is also exploring the use of OCT and spectroscopy in the treatment of heart arrhythmias.

Other projects running in Hendon’s Structure Function Imaging Laboratory include using optical tools to detect and image breast cancer and using imaging to assess the mechanical properties of the cervix in relation to preterm birth.

“For a young researcher, this is the pinnacle of recognition, and I am thrilled to be included in this brilliant group, said Hendon, assistant professor of electrical engineering. “It is wonderful to see the White House acknowledging scientific accomplishments from investigators working on a diverse array of problems.”

Previous Columbia Engineering professors to receive the PECASE include Antonius “Ton” Dieker, associate professor of industrial engineering and operations research (2016); Jose Blanchet, professor of industrial engineering and operations research (2010); Helen Lu, professor of biomedical engineering (2009); Xi Chen, associate professor of earth and environmental engineering (2007); and Jeffrey Kysar, chair and professor of mechanical engineering (2006).


Columbia Engineers Develop New, Low-Cost Way to Capture Carbon
By confining water in tiny pores too small to see without a microscope, a team of researchers has discovered a new way to capture carbon dioxide (CO2) from the atmosphere more efficiently and at a much lower cost than other methods. The team, led by Xi Chen, associate professor of earth and environmental engineering at Columbia Engineering, and Klaus Lackner of Arizona State University, discovered an unconventional reversible chemical reaction in the confined nanoenvironment. The discovery, a milestone in clarifying the scientific underpinnings of moisture-swing chemical reaction, is critical to understanding how to scrub CO2 from Earth’s atmosphere.

Water is the key player. The group found that reducing water quantities in nanoconfinement could promote carbonate ions (CO3 2-) to hydrolyze water (H2O) into a larger amount of hydroxide ions (OH-).

The discovery led to a new nanostructured CO2 sorbent that binds CO2 spontaneously in ambient air when the surroundings are dry and releases it when exposed to moisture. The mechanism of the moisture-swing chemical reaction in nanopores could lead to new classes of sorbents driven by water: evaporation in ambient air through solar energy drives the sorbent to absorb CO2 as it dries, and hydration releases CO2 when wet. The estimated cost of capturing CO2 from air could be lower than that of any other carbon-capture technology, enabling negative carbon emissions, Chen said.

Chen, whose research focuses on the mechanics of nanoporous materials, has long been interested in studying fundamental interactions between water and ions in confined spaces. When confined to nanopores, the hydrogen bonding of water and ions changes, affecting both the physical structure and dynamics of water molecules and also the chemical energy transfer through the formation of highly structured water complexes.

“Water is the most magical substance in the world—it produces life,” Chen says. “Its hydrogen bond is incredibly strong—except, as we discovered, when you have a very small environment with very few molecules. Then everything changes, and we were able to actually reverse chemical reactions when the number of water molecules fell below about 10.”

Chen’s team, including PhD students Xiaoyang Shi and Hang Xiao, also found that the humidity-driven sorption effect is extendable to a series of ions, suggesting a new approach to gas separation technology.


New Method Extends Life of Lithium Batteries
When today’s lithium ion batteries are charged for the first time to power smartphones or electric vehicles, they lose 5 to 10 percent of their capacity, and the loss is even higher for some ﻿﻿materials currently being investigated for next-generation batteries. Yuan Yang, an assistant professor of materials science and engineering, saw a way to cut those losses significantly and produce batteries that last longer.

The trick is in the structure and a special protective coating. Yang has developed a trilayer structure that is stable even in moist ambient air. His new design could improve the energy density of lithium batteries by 10 to 30 percent.

“We think our method has great potential to increase the operation time of batteries for portable electronics and electric vehicles,” Yang said.

During the first charge of a lithium battery after its production, a portion of liquid electrolyte is reduced to a solid phase and coated onto the negative electrode of the battery. This process, usually done in the factory before the battery is shipped, is irreversible and lowers the energy stored in the battery. The loss is approximately 10 percent for state-of-the-art negative electrodes, but it can reach 20 to 30 percent for next-generation, high-capacity negative electrodes, such as those containing silicon, because the materials have large volume expansion and high surface area. The large initial loss reduces the capacity in a full cell and thus compromises the gain in energy density and cycling life of these nanostructured electrodes.

The traditional approach to compensating for this loss has been to put certain lithium-rich materials into the electrode; however, most of these materials are not stable in ambient air. Manufacturing batteries in dry air, which has no moisture, is a more expensive process than manufacturing in ambient air.

Yang’s new trilayer electrode structure protects the lithium with a layer of the polymer PMMA, to prevent lithium from reacting with air and moisture, and then coats the PMMA with active materials such as artificial graphite or silicon nanoparticles. The PMMA layer dissolves in the battery electrolyte, exposing the lithium to the electrode materials.

“This way, we were able to avoid any contact between unstable lithium/lithiated electrode and air, so the trilayer-structured electrode can be operated in ambient air,” Yang explained. “This could be an attractive advance toward mass production of lithiated battery electrodes.”

Yang’s method lowered the loss capacity in state-of-the-art graphite electrodes from 8 to 0.3 percent, and in silicon electrodes from 13 to -15 percent. The negative number indicates that there was more lithium than needed. That “extra” lithium could be used to further enhance the cycling life of batteries by compensating for capacity loss in subsequent cycles.

Yang’s group is now trying to reduce the thickness of the polymer coating, so it will occupy a smaller volume in the lithium battery, and to scale up use of his technique.


Photo courtesy of John Allen

Increasing Tornado Outbreaks—Is Climate Change Responsible?
Tornadoes and severe thunderstorms kill people and damage property every year, with the heaviest tolls often coming during tornado outbreaks, when dozens of twisters strike in close succession.

Last spring, a research team led by Michael Tippett, associate professor of applied physics and applied mathematics at Columbia Engineering, published a study showing that the average number of tornadoes during outbreaks has risen since 1954. But they were not sure why.

They looked at trends in the severity of tornado outbreaks, where they measured severity by the number of tornadoes per outbreak. They found that these upward trends are increasing fastest for the most extreme outbreaks. While they saw changes in meteorological measurements that are consistent with these upward trends, the trends in meteorological changes were not the ones expected under climate change.

“This study raises new questions about what climate change will do to severe thunderstorms and what is responsible for recent trends,” Tippett said. “The fact that we don’t see the presently understood meteorological signature of global warming in changing outbreak statistics leaves two possibilities: either the recent increases are not due to a warming climate, or a warming climate has implications for tornado activity that we don’t understand.”

Better understanding of how climate affects tornado activity could help predict tornado risk in the short-term, a month, or even a year in advance.

The researchers used two NOAA (National Oceanic and Atmospheric Administration) data sets: one containing tornado reports, and the other observation-based estimates of meteorological measurements associated with tornado outbreaks. Using extreme-value analysis, they found that in the United States, the frequency of outbreaks with many tornadoes is increasing, and it is increasing faster for more extreme outbreaks.

Extreme meteorological environments associated with severe thunderstorms showed consistent upward trends, but the trends did not resemble those currently expected to result from global warming. Modeling studies have projected that convective available potential energy will increase in a warmer climate leading to more frequent environments favorable to severe thunderstorms in the United States. However, the researchers found that the meteorological trends were instead consistent with trends in storm-relative helicity, a measure of wind shear, which has not been projected to increase under climate change.


Professor Steve WaiChing Sun Wins Air Force’s Young Investigator Program Award
Steve WaiChing Sun, assistant professor of civil engineering and engineering mechanics, has won a prestigious Young Investigator Research Program (YIP) grant from the Air Force Office of Scientific Research.

The three-year, $360,000 grant will support research to help understand how wet granular materials, such as sand and sediment, respond to the impact of blasts, subsurface explosions, and mining activities; and also research into the ballistic vulnerability of military structures.

Sun also added a twist to his proposal: he plans to use 3D printing and open-source code so his work can be replicated and validated by other researchers.

“Granular material is the second most-handled material in the global industry—second only to water—so the fundamental knowledge we gain will have far-reaching consequences, from helping engineers make more efficient and safer designs for mining and containment of underground explosions to assessment of earthquake damages,” Sun said. “It is essential that we foster collaboration because that is how we will advance our field.”

Sun works in the fields of theoretical and computational solid mechanics, poromechanics, and multiscale modeling of fully coupled multiphysical systems, looking to improve predictions of large-scale field problems with insight from small-scale observations and simulations. His research is focused on advancing the understanding of multiphase materials under extreme conditions and expanding predictive capabilities for related engineering applications, including geological carbon sequestration, hydraulic fracturing, and nuclear waste disposal.

His proposal was selected from among more than 230 to the YIP, which fosters creative basic research in science and engineering and the development of outstanding young principal investigators. In 2015, Sun also received the U.S. Army’s Young Investigator Program award to model how microscopic water and air seepages inside each pore of granular materials affect the stability of the ground.

Additionally, Sun recently won a three-year, $800,000 grant from the U.S. Department of Energy’s Nuclear Energy University Programs to study the thermal-mechanical-hydrologic-chemical coupling effect on the reconsolidated salt-clay mixture used for underground nuclear waste disposal.


Professor Paul Sajda Named an AAAS Fellow
Paul Sajda, professor of biomedical engineering, electrical engineering, and radiology, has been named a fellow of the American Association for the Advancement of Science (AAAS) for his “distinguished contributions to the understanding of neural correlates of vision, human perceptual decision-making, and cortically coupled computer vision.”

He joins three other Columbia faculty members who are among 391 new fellows awarded the honor this year for their advances in science or its application.

Sajda’s research is focused on neural engineering, an emerging interdisciplinary field that uses engineering techniques to understand and interface with the brain. He uses large-scale computational modeling, machine learning, and advanced neuroimaging to investigate the function and manipulate the behavior of the human central and peripheral nervous systems.

His work has led to the development of several innovative systems under what he terms “applied neuroscience,” including brain computer interfaces for image search and expertise assessment. Three startups have emerged from his Laboratory for Intelligent Imaging and Neural Computing at Columbia, focused on commercializing neurotechnology in market areas ranging from sports to neurogaming to autonomous driving.

Of being named an AAAS fellow, Sajda said: “Of course, this honor would not have been possible without the group of outstanding students, postdocs, and colleagues I have had the privilege to work with while here at Columbia and throughout my career. I am proud to share this honor with them.”

Four other Columbia Engineering professors have received the honor: Shih-Fu Chang, senior executive vice dean, Richard Dicker Professor of Telecommunications, and professor of computer science (2010); Aron Pinczuk, professor of applied physics and physics (2001); Peter Schlosser, Earth and Environmental Engineering Department chair, Maurice Ewing and J. Lamar Worzel Professor of Geophysics, and professor of earth and environmental sciences (2010); and Gordana Vunjak-Novakovic, Mikati Foundation Professor of Biomedical Engineering and professor of medical sciences (2014).

By Holly Evarts