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.

Closed-Loop Control System for Plasma Medicine

The Plasma for Life Science group is working to develop a closed loop control system that can be used to deliver a regulated and reliable plasma dose to a target given real-time sensor feedback. Cold atmospheric pressure plasmas have shown great promise for the treatment of wounds and cancerous tumors given specific voltage, frequency, and treatment time setpoints. Cold atmospheric plasms are beneficial for medical applications as they produce reactive species and other molecules when treating biological samples that can be detected through chemical biosensors. By determining the concentration of species produced from defined settings in a microsecond pulsed plasma, the Plasma for Life Sciences group hopes to establish real time feedback control to accurately regulate and determine the correct plasma treatment or safety thresholds for wound healing and other applications. This project is funded by NIH grant R01EB029705.

Researchers: Jonathan Thomas, Eirini Klemes, Jordan Simpson

Plasma-treated Water for Agriculture

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, Sophia Carson, Caleb Smith

Plasma/Liquid Interactions in Bubbles

Investigating the breakdown phenomena in multiphase (plasma-air-liquid) systems, this research examines streamer propagation and plasma regime classification through both computational models and experimental setups. Influential parameters such as bubble morphology, electrode spacing, voltage pulse parameters (rise time, peak voltage, and duration), and the dynamics of liquid-gas interactions at the electrode’s vicinity are scrutinized for their roles in the breakdown process. Imaging techniques capable of capturing bubble dynamics at nanosecond resolutions are employed, focusing on bubbles created by gas injection as well as those resulting from cavitation.

Three-dimensional simulations of bubble shape and flow dynamics are conducted using the PHASTA computational fluid dynamics software, while electrical breakdown phenomena within the gas bubbles and along the liquid-gas interface are modeled in two dimensions with nonPDPSIM, providing comparative analysis against experimental data.

Plasma/liquid interactions at the gas/liquid interface are leveraged for spectroscopic investigations to discern the chemical composition within the bulk liquid, laying the groundwork for advanced diagnostics in the characterization of liquid.

This research is part of a collaborative effort with Dr. Bolotnov’s Multiphase Research Group, supported by NSF Grant No. PHY 2107901. Concurrently, the Plasma-Bubble Spectroscopy project is conducted in association with Dr. Bataller’s Ultrafast Spectroscopy Group, under the NEUP Project 21-24307. The overarching study is further bolstered by the support from the Nuclear Energy University Program (NEUP) through a Graduate Student Fellowship, underscoring its commitment to fostering innovation in nuclear science and technology.

Current Researchers: Nicholas Sponsel, Kristina Pattison

Former Researchers: Dr. Naveen Pillai (computational)

Non-Oxidative Plasma-Driven Mechanisms for PFAS Destruction

Per- and polyfluoroalkyl substances (PFAS) are a class of man-made chemicals commonly found as harmful contaminants in groundwater. PFAS have been linked to a wide array of health effects in both humans and animals including liver damage, thyroid disease and cancer. These compounds are characterized by strong carbon-fluorine bonds and are very hard to break down via traditional water treatment methods. This project seeks to expand upon previous work that has shown plasma treatment as an effective technique for aqueous PFAS destruction. We investigate the reaction pathways of non-oxidative species produced in the gas phase of a dielectric barrier atmospheric pressure plasma jet (APPJ) as these species are theorized to dominate PFAS breakdown. Additionally, a COST-Jet is employed to examine the impact of photons and other uncharged particles on non-oxidative chemistry in a liquid substrate. Particular attention is paid to the production of ions, metastable atoms, and solvated electrons. Analysis is predominantly carried out using optical emission spectroscopy (OES). Both plasma sources are operated using different feed gasses and power supply parameters. This work is conducted in collaboration with Dr. Selma Mededovic’s group at Clarkson University and Dr. Arthur Dogariu’s group at Texas A&M University. The research is supported by the National Science Foundation under NSF grant PHY 2308857.

Researchers: María J. Herrera Quesada, Caleb Smith

Generation and Transport of Reactive Species for Plasma Medicine

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, we investigate biologically-relevant RONS (e.g. OH, H2O2, NO..) produced by the NTP source COST-Jet (European Center Of Science and Technology atmospheric pressure plasma jet) on substrates such as amino acids, enzymes, cell media, and cells. Current experimental diagnostic techniques include FTIR (Fourier Transform Infrared) Spectroscopy, Mass Spectrometry, Raman Spectroscopy, Photometric Assays, and EPR (Electron Paramagnetic Resonance) Spectroscopy, and LIF (Laser Induced Fluorescence). These studies will help us find efficient plasma source parameters for RONS transport and ultimately help tailor plasma sources used for medicine. This work has been funded by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences Opportunities in Frontier Plasma Science program under Award Number DE-SC-0021329, the UNC Lineberger Cancer Center, and NIH project R01EB029705.

Researchers: María J. Herrera Quesada 

Surface Modification of Plasma-Treated Human Surrogate Skin

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

Characterization of Dielectric Barrier Discharges

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

0D Kinetic Modeling of Nanosecond Pulsed Discharge

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