Katharina Stapelmann

Plasma medicine is a rapidly emerging field that encompasses the biomedical applications for cold plasma (a.k.a. non-thermal, non-equilibrium, or atmospheric plasma). Cold atmospheric plasma (CAP) is generated by using an electromagnetic field to ionize a gas at atmospheric pressure and temperature. When applied to living cells or tissues, cold plasma can produce a spectrum of effects, from subtle changes in cellular metabolism/function to programmed or necrotic cell death. This suggests that cold plasma delivery can be controlled to achieve a predetermined cellular change. Therefore, one critical question about interactions between cold plasma and human cells/tissues concerns the plasma ????????????????dose??????????????? necessary to achieve a desired clinical outcome without adverse side effects. Plasma dose may be controlled by altering parameters that affect plasma generation (including voltage and frequency), varying the exposure duration or distance, changing the feed gas, and selecting a plasma device suitable for the specific application. At present, the assessment of the effects of regulated clinical plasma delivery relies upon measures of outcomes that assess secondary or tertiary responses hours or even days after the exposure. There are no immediate indicators to guide the clinician during treatment. There is a critical need for identification of markers that correlate biological and clinical outcomes with the capability of real-time measurements. The proposed studies will address this by pioneering the development of real-time detection strategies for plasma-based therapies, using plasma-facilitated wound repair as the disease model. We and others have shown that cold plasma enhances and accelerates wound healing processes in vitro and in vivo. Our focus on real-time detection will facilitate the development efforts for this specific therapeutic use of plasma and provide the foundation for extending this strategy to other clinical applications of plasma.

The goal of this research program is to gain fundamental understanding of the multi-phase plasma-gas-liquid system by utilizing both theoretical and experimental approaches. The plasma breakdown and streamer development in steep gradients will be investigated dependent on realistic bubble geometries and as a function of applied voltage conditions. The multiphase interface tracking DNS code PHASTA has been well-established through a wide variety of two-phase flow problems. When coupled with the well-established plasma modeling and characterization code nonPDPSIM, it will give new insights into gas bubble formation and how the size and shape of the bubbles will influence the breakdown of the plasma. The experiment will allow the production of various well-defined bubble shapes and sizes, making it possible to investigate the dependency of the plasma breakdown on bubble geometries. The project will provide 1) the initial steps to combine high-resolution multiphase physics with electric fields and plasma physics, opening the opportunity to study fundamental plasma physics in a multiphase system, and 2) the experimental investigations to benchmark the simulations and to study how the polarity of the applied voltage pulses affects the streamer propagation in a bubble in liquids.

The aim of this research is to capture time- and space-resolved behavior of breakdown initiation and development in water with gas bubbles injected between the electrodes when excited with microsecond voltage pulses. The results will be directly compared to our previous results from a PCRF collaboration on the development of an electrical discharge in a gas bubble immersed in liquids with different conductivities when excited by nanosecond voltage pulses. For nanosecond regimes, cavitation seems to play a major role in plasma breakdown for low conductivities and discharge initiates at an electrode. On microsecond timescales, where cavitation does not play a role, it has been hypothesized that breakdown in water occurs first in bubbles on or near the electrodes, pre-existing or formed thermally. Hence bubble injection is expected to influence discharge initiation. Much of the recent work has been focused on shorter (nanoseconds) and longer (>100 microseconds) time scales. As part of a DoE-NEUP fellowship project, we are developing the capability to perform optical emission spectroscopy in gas bubbles immersed in molten salt. In another project, we are using gas bubbles immersed in water to fix nitrogen and produce N fertilizer on demand. For both projects, the capture of spatial and temporal resolution of streamer propagation and spectra is fundamental. By imaging the streamer propagation in bubbles in liquids we aim to determine 1. The difference in breakdown initiation on microsecond and nanosecond time scales with and without injected gas bubbles 2. Whether the injected bubbles influence discharge initiation at the microsecond time scales.

Our goal is to develop an innovative in-package plasma manufacturing technology for improving safety, maintaining quality and nutrients, and extending shelf-life of fresh produce while being energy, water, and resource-efficient.

Enabling the next generation of sustainable farms requires a paradigm shift in resource management of the two most critical agricultural inputs for food production: water and nitrogen (N) - based fertilizer. Inefficient management of these resources increases food production costs, decreases productivity, and impacts the environment. An integrated approach is needed to improve the sustainability and efficiency throughout the production chain. Emerging (bio)electrochemical (BEC) technologies offer alternatives to conventional, fossil-fuel intensive N fertilizer production. Recently our team has demonstrated two game-changing BEC technologies: 1) microbial conversion of nitrogen gas into ammonium, and 2) plasma generation of N species (e.g., nitrate, nitrite) and other reactive species in water for fertilization and anti-pathogen benefits. We will integrate these technologies to produce BEC, N-based fertilizer, and with advanced sensor and delivery systems, we will precisely supply fertilizers for sustainable precision agriculture. Our proposed approach focuses on the development of a novel ????????????????BEC fertigation on demand system??????????????? by using sensor-driven data and molecular analyses to investigate BEC fertigation impact on the plants?????????????????? growth, adaptation, and microbiome; its impact on food safety and quality, and its economic feasibility for on-farm deployment.