Current Research
Non-thermal or cold atmospheric plasma is an alternative method to produce biologically relevant chemical species. We manipulate the plasma discharge parameters to selectively produce specific species and tailor them to life science applications.
Non-thermal Plasma
| Non-thermal plasma (NTP) is a partially ionized gas where the electrons are considered thermal, or high energy, while the surrounding gas molecules are at or around room temperature. Our lab specializes in the generation and characterization of these plasmas. We modify our approach to apply plasma based on the chemical makeup of the substrate, e.g. skin, cells, water, plants, etc. The mechanisms behind how plasma components (UV, high electric field, generated reactive species) directly influence these substrates for cancer treatment, wound healing, increase in seed germination, and sterilization are still under investigation. To understand how to optimize plasma treatments for these applications, we measure the transport and delivery of plasma-generated reactive oxygen and nitrogen species in the plasma, gas, liquid and solid phases through spectroscopy (OES, UV-Vis absorption, FTIR, Raman, Electron paramagnetic resonance) and mass spectrometry. We then engineer plasma devices to investigate plasma-liquid interactions, improvements for plasma-based therapy, or enhanced species transfer for plasma-based fertilizer. |
Plasma Treated Water for Agriculture
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At the core of species transport from the plasma phase through the liquid phase is the interaction between the plasma-liquid interface. Rate of change of the pH, conductivity, and chemical species solvated in the liquid phase are dependent on the surface area to volume ratio between the plasma and liquid phase. Supplying adequate nitrogen is essential for plant fertilization. Different reactive nitrogen & oxygen species (RONS) are also important signaling species for the health and growth of the plant. Our lab is investigating several plasma devices to characterize both the species content and concentrations, as well as energy efficiencies to aid in on-demand Plasma Treated Water (PTW) fertilizer for greener means to crop-tailored agriculture. Plasma effluent transported through bubbles, as well as direct plasma breakdown in bubbles, are utilized to increase the surface-area-to-volume ratio of the gas/liquid interface at which RONS transport occurs. This research is carried out in collaboration with the interdisciplinary research team funded by the Game-Changing Research Incentive Programs for the Plant Science Initiative (GRIP4PSI) here at NCSU.
Researchers: Conner Robinson, Nicholas L. Sponsel, Tanjina Akter |
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Plasma/Liquid Interactions in Bubbles
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To better understand the breakdown behavior across multiphase (plasma-air-liquid) systems streamer propagation and plasma regime type are investigated through both computational and experimental perspectives. Parameters such as bubble shape & deformation, electrode proximity, voltage pulse-width, and voltage rise-time impact the breakdown through the gas bubble, along the liquid-gas interface, and liquid-gas expansion at the electrode interface. Gas injected bubbles, as well as thermal-expansion bubbles, are imaged at both nanosecond and microsecond timescales. Bubble shape and flow are simulated in 3-dimensions with PHASTA and electrical breakdown is 2-dimensionally modeled and compared to experiment using nonPDPSIM. Plasma/liquid interactions occurring at the gas/liquid interface are utilized for spectroscopic analysis of the chemical content of the bulk liquid. This is preliminary research in advanced diagnostics for molten salt material characterization. The computational/experimental research is carried out in collaboration with Dr.Bolotnov’s Multiphase Research Group under NSF Grant No. PHY 2107901. The Plasma-Bubble Spectroscopy research is being pursued in collaboration with Dr.Bataller’s Ultrafast Spectroscopy Group under NEUP Project 21-24307. This research is supported by the Nuclear Energy University Program (NEUP) Graduate Student Fellowship.
Researchers: Nicholas L. Sponsel, Naveen Pillai, JT Mast |
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NO Transport in Biological Substrates
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Nitric oxide (NO) is known to enhance wound healing and sterilization applications. Specifically, NTP treatment has been shown to be effective for chronic wounds, cancer, and even antibiotic-resistant bacterial infections. Although the positive effects of NTPs are well documented, the underlying chemical and biological mechanisms are still not well understood due to the inherent complexity of plasma components (electric fields, UV radiation, and reactive chemical species) and their effects on biological substrates. Among the myriad reactive species that are produced in NTPs, NO is theorized to play a crucial role in these applications. Research has shown that NO restricted bioavailability is one of the main causes of complications in wound healing, infections, and decreased tissue microcirculation. We investigate NO-rich gas admixtures produced by the NTP source COST-Jet (European Center Of Science and Technology atmospheric pressure plasma jet) on biologically relevant substrates such as amino acids, enzymes, cell media, and cells. Current experimental techniques include FTIR (Fourier Transform Infrared) Spectroscopy, Mass Spectrometry, Raman Spectroscopy, Photometric Assays, and EPR (Electron Paramagnetic Resonance) Spectroscopy. These studies will help us find efficient plasma source parameters for NO transport and ultimately help tailor plasma sources used for medicine.
Researchers: María J. Herrera Quesada, Cameron Wagoner |
Surface Modification of Plasma-Treated Human Surrogate Skin
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The implementation of plasma therapy is limited due to insufficient information for establishing a correct ‘dose’. To understand how to select a suited ‘dose’, we focus on answering two major elements: 1) the physical penetration depth of plasma components, and 2) the penetration depth of the plasma-induced effects. Using 3-dimensional Raman spectroscopy, we identify modifications in plasma-treated human surrogate skin to track the physical depth of penetration and radial distribution of plasma-generated RONS for given discharge parameters.
Researchers: María J. Herrera Quesada |
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Characterization of Dielectric Barrier Discharges
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Dielectric barrier discharges (DBDs) rely on their ability to produce reactive species from the ambient environment for applications such as ozone creation to biological applications such as wound healing, disinfection, and cancer therapy. While most are used at low pressure, the development of DBDs that operate at atmospheric pressure is useful to life science applications where low-pressure environments are not feasible. The Plasma for Life Science group is studying the breakdown and electrical characteristics of both volume and surface DBDs for the purpose of optimization, in terms of high chemical efficiency with low gas heating and power consumption. With the help of collaborators at Rutgers University and the food science department at North Carolina State University we are developing and optimizing flexible surface DBD electrodes that can be used in a variety of package applications. The effects of plasma treatment on fresh produce are also being investigated.
Researchers: Duncan Trosan, Pat Walther |
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0D Kinetic Modeling of Nanosecond Pulsed Discharge
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A computational project dedicated to modeling DBD discharges. Experimental data from the characterization of volume and surface DBD project is used as input data for the ZDPlaskin modeling software. In addition, gas-phase chemistry measurements in molecules such as ozone and NO will be used to help verify the results of the code. This project will enable the estimation of other gas-phase products and help contextualize the experimental results.
Researchers: Duncan Trosan, Pat Walther |
