Where Can LIBS Make the Biggest Impact?

For an emergent analytical technique to be adopted, its proponents must find applications where it offers significant benefits over established techniques, such as sensitivity, speed, cost, or ease of use, or some combination of those. For laser-induced breakdown spectroscopy (LIBS), identifying its ideal niche has been one of the challenges in gaining followers. To assess where LIBS is being used today, what new areas are emerging, and how well LIBS competes with other methods in those new areas, we asked a panel of experts for their views.

Richard R. Hark, the H. George Foster professor in the Department of Chemistry at Juniata College and Chief Scientist at Synergos Global Security, noted that LIBS has already found broad application as a tool for materials analysis in a variety of industries ranging from recycling of scrap metals and plastics to analysis of coal, foundry metals, and electronic components. As for emerging areas in which LIBS will likely have an impact, he sees promise in biomedical testing, forensics analysis, identification of hazardous materials, and examination of geological and environmental samples. "LIBS analysis will continue to expand in laboratory and industrial settings, but as field analysis applications mature, LIBS will be a superior single instrument, and uniquely capable when fused with other sensor modalities," he predicted.

Rick Russo, a senior scientist at Lawrence Berkeley National Laboratory and president and CEO of Applied Spectra, agreed that LIBS is gaining acceptance in many industrial applications and continues to receive significant research emphasis around the world. "Geology, ecology, forensics, pharmaceuticals, semiconductors, consumer electronics, metallurgy, mining, photovoltaics, and battery applications are seeing good returns using this technology," he said. He added that new areas exist for standoff measurements and real-time continuous process monitoring in industry, such as in raw-material or product screening for impurities and contamination.

Steven J. Rehse, an associate professor in the Department of Physics at the University of Windsor, is a big proponent of using LIBS in medical applications, which is the primary focus of his research. "I believe that the trends in 21st century medicine to perform faster, cheaper, and less-invasive procedures perfectly complement the advantages that LIBS brings to the table," he said. Just as industry has seen that this technique can be used for real-time quality assurance and process monitoring, he envisions LIBS assays being used in a host of medical and biomedical procedures for rapid tests performed at the "point of contact" -in a doctor's office or clinic. "In many of the areas that I am describing there are no other methods being used at all, and that is where LIBS could make an immediate impact," he said.

Rehse mentioned two examples of such applications. The first was related to how lasers are already being used to "drill" cavities in teeth prior to filling. It has been shown that the LIBS emission from such a tooth can be used to clearly differentiate healthy tooth tissue from the cavity (the carious tissue). "Yet as far as I know, this technology has not been adopted, and so instead a dentist uses no technology and just goes by training and experience to decide how much tissue to remove," he said.

The second example is the use of LIBS emission during transcranial surgery to monitor how deeply into the skull the surgeons are cutting (3,4). "They have been able to leave an extremely thin (basically transparent) but intact 'window' of skull bone over the brain and perform optical procedures in the brain through that window without ever exposing it to the environment," he said.

In Rehse's own field of microbiological identification, he said, the speed of LIBS tops all the competing techniques that are based on genetic identification, serological (antibody-based) identification, or other principles. "LIBS will probably never perform as well as the gold-standard culturing techniques, and it may not be as sensitive as a genetic 'real-time' polymerase chain reaction (PCR) test, but it is fast enough to begin directing treatment immediately, suggest other tests that could be run, or even just confirm whether or not bacteria are present-in a simple 'yes or no' test that does not require true identification," he said.

Vincent Motto-Ros, an associate professor at the Light and Matter Institute at Lyon University, agreed that biology and medicine are emerging application areas for LIBS. "We have been working for several years in my institute on the development of LIBS for elemental imaging of biological tissue," he said. "With its all-optical design and its parts-per-million scale of sensitivity, LIBS imaging is unique among methods of elemental detection because of its full compatibility with standard optical microscopy." Motto-Ros explained that the biomedical community is very enthusiastic about the imaging capability of LIBS because current methods for the observation of trace elements in tissues at microscopic spatial resolution often require complex equipment with restricted access.

Ishan Barman, an assistant professor in the Departments of Mechanical Engineering and Oncology at Johns Hopkins University, said that an intriguing route to pursue would be the engineering of LIBS tags for biomarker characterization. "Next-generation cancer diagnostics, particularly in the form of 'liquid biopsy,' represents a huge opportunity where LIBS can make a substantive difference," he said. Nevertheless, Barman explained, a number of the biomarkers (notably tumor antigens shed into the vasculature) may not be detected with high specificity using only LIBS-based elemental analysis. "Incorporating biomarker-specific tags (with suitable recognition moieties and LIBS-active elements) may allow LIBS to penetrate into hitherto unexplored territory," he concluded.

Another emerging area of application for LIBS is energy applications, explained Vassilia Zorba, a staff scientist at Lawrence Berkeley National Laboratory. "The application of LIBS to electrochemical energy storage technologies such as lithium-ion batteries will be particularly important because of its sensitivity to lithium and its spatially resolved and depth-resolved chemical imaging capabilities," she said. "These features will bring a new dimension to chemical analysis that is lacking in energy dispersive X-ray spectroscopy and ICP-OES, which are the commonly used techniques in lithium-ion battery research currently."

In China, coal, metallurgy, and cement applications have a very large market in LIBS, noted Zhe Wang, an associate professor at Tsinghua University. "Environmental protection is also an emerging application, but right now LIBS is not as good as XRF," he added.

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This article is an edited excerpt of “Analysis of the State of the Art: LIBS.”

The article is part of a special group of six articles covering the state of the art of key techniques, also including inductively coupled plasma–mass spectrometry (ICP-MS), X-ray fluorescence (XRF) spectroscopy, infrared (IR) spectroscopy, near-infrared (NIR) spectroscopy, and Raman spectroscopy.