Madhavi Martin brings a physicist’s tools and perspective to biological and environmental research at the Department of Energy’s Oak Ridge National Laboratory, supporting advances in bioenergy, soil carbon storage and environmental monitoring, and even helping solve a murder mystery.
Martin’s research revolves around the interaction of light and matter, leveraging a technique called laser-induced breakdown spectroscopy, or LIBS, that gives scientists the ability to rapidly produce an exact “chemical fingerprint” of a sample.
LIBS uses a laser pulse to create a spark with a miniscule amount of plasma from the material being examined. The plasma emits light at wavelengths unique to the elements present, and the spectral output is processed by a computer. The technique requires little sample preparation and can deliver chemical composition results in near-real time.
While LIBS is most widely used in materials science and in industrial process monitoring, it has also become a popular tool for applications such as medical research and to detect painting forgeries.
Martin, lead for the lab’s Biomaterials and Biomass Characterization group, has used LIBS to detect concentrations of elements in plants and soil that can affect how plants grow and store carbon. Another project helped scientists identify the gene that triggers silicon accumulation in poplar leaves and linked it to cellulose biosynthesis, which relates to biofuels production and carbon sequestration. She also used LIBS to determine how much ash and inorganic material are present in switchgrass, which could affect how the plant’s biomass is broken down and converted into renewable fuels.
She suggested that the lab try the LIBS technique to monitor aerosol emissions at a coal-fired power plant, which led to one of her first big projects. The work was initiated when Martin was a postdoctoral researcher under the mentorship of Mengdawn Cheng, a distinguished scientist who specializes in aerosols research at ORNL. The work was highly successful, yielding large amounts of data and establishing a new paradigm in environmental monitoring.
Segue into biology, environmental science
“That project got me thinking about using LIBS for solid samples like soils, and that research was also successful. When that work became known, it attracted other collaborators who wanted to test the technique on bacteria and then plant leaves, roots and wood samples,” Martin said. By separating out chemical elements with LIBS, Martin could determine, for instance, the different species of trees in a variety of geographical areas that grow naturally in different soils and environments and even the weather conditions in which the trees grow. The findings have factored not only into ORNL’s bioenergy research but also into its climate change science, including how trees respond to controlled burns and wildfire.
“I never imagined in my wildest dreams that being a pure physicist could lead me into such an interesting research area,” Martin said. Now an internationally recognized expert in the use of LIBS for biological and environmental applications, Martin said that especially early in her career, her fellow scientists at academic conferences were often surprised to hear her present on life science applications for LIBS. They often assumed that seeing the topic and ORNL on the agenda meant that she was presenting about nuclear forensics or other materials science.
It was another type of forensics research that resulted in Martin’s most unusual project to date. A professor at the University of Tennessee, Knoxville, had been asked to advise on a murder case. He thought of Martin’s work with wood chemistry and asked her to use LIBS to analyze several wood samples. Unbeknownst to Martin at the time, the logs had been confiscated by Texas police at a crime scene.
Police suspected that some of the same logs used to burn a murder victim’s body in a remote area were later transported and used in a fire pit at a party attended by the suspect. In analyzing the samples, Martin found that the elemental makeup of the logs matched. That and other forensic evidence resulted in a conviction in the case.