Session GT53: Plasma Agriculture

High-Quality Manufacturing of Packaged Fresh Produce with Conformable In-Package Cold Atmospheric Plasma

Atmospheric pressure plasma has been shown to aid in food decontamination due to the presence of reactive oxygen and nitrogen species. In the past, this application has been limited due to high voltage requirements and the need for rigid electrodes that do not conform to the complex geometries of produce. A conformable low-cost dielectric barrier discharge device was developed to operate inside containers and deliver reactive oxygen and nitrogen species to the produce.¹ These flexible electrodes need to be characterized to better understand the gas-phase chemistry being produced and transported to the surface of the produce. The devices are electrically characterized to find the discharge current and dissipated power. They are also analyzed using absolutely calibrated optical emission spectroscopy to find plasma parameters.² These devices have also been shown to have antibacterial effects on both cells in culture and on the surface of produce. Cell culture experiments have shown a 6 log reduction in L. innocua bacteria. These results will be used to modify and optimize the design of the flexible electrodes with the goal of minimizing energy consumption and maximize decontamination efficiency. 

 

[1] Jingjin et al. Proceedings of the National Academy of Sciences, 2017.

[2] Kogelheide et al. Plasma Processes and Polymers, 2019.    

Cold plasma interactions with the Venus flytrap: Electrophysiology and side effects

Cold atmospheric pressure radio frequency plasma (CAPP) can play an important role in agriculture, medicine, biophysical and bioelectrochemical applications, disinfection and sterilization, synthesis of different compounds, nitrogen fixation, and treatment of surfaces. Here we found that reactive oxygen and nitrogen species, UV-Vis photons, and high-frequency strong electromagnetic fields with an amplitude of a few kV produced by a cold plasma jet can interact with bio-tissue and damage it if the plasma treatment is long enough. The electrophysiological effects of CAPP treatment of bio-tissue and electrical signals transmission were measured in the Venus flytrap. The plasma ball does not produce any visible side effects on the Venus flytrap, but induces electrical signals in bio-tissue with very high amplitude. Plasma (Kirlian) photography shows the existence of a blue aura around the plasma ball due to a corona discharge. Understanding the mechanisms of interactions between CAPP and bio-tissue and preventing side effects can contribute to the application of plasma technology in medicine and agriculture. The use of cold plasma in medicine and agriculture should be monitored for side effects from strong high-frequency electro-magnetic fields, UV photons, and reactive oxygen and nitrogen species to protect against undesirable consequences.   

Characterization of the Plasma Apparatus to Develop and Advance the Plasma-based Depyrogenation Process

Endotoxin deactivation using plasmas has been demonstrated at levels that enables plasma treatment to be classified as a medical depyrogenation device per FDA guidelines. Depyrogenation efficacy was evaluated for synthetic air, nitrogen, and helium plasmas and a 4-log reduction in endotoxin levels was achieved with 30 minutes of treatment. This development of a cost-effective system and identification of the mechanisms that drive plasma-based depyrogenation are in the preliminary stages, but have yielded promising results. Synthesizing endotoxin free chitosan polymer is a challenge for the use of chitosan for internal medicine and drug delivery. A dielectric barrier discharge has been built to perform depyrogenation inside hermetically sealed bags. The FDA requirement for depyrogenation processes is a 3-log reduction in endotoxin levels. Along with demonstration of a 4-log reduction, this study looks at the post-plasma treatment modifications in the chitosan polymer and surface modifications of different bag materials (low-density polyethylene, Nylon, and Teflon FEP) using FTIR and Raman spectroscopy. Measurements for the applied power, bag surface temperatures, optical emission spectroscopy, and gas temperatures were carried out to characterize the plasma apparatus.   

Low temperature Plasma processing for fabricating metal nanoparticles coated antimicrobial surfaces for potential biomedical applications

Plasma surface modification is a facile surface modification technique that has been employed for decades for modifying the surface properties of biomaterials. The nondestructive and in-situ sterilization capabilities of this technique make it an attractive candidate for modifying the surface properties of biomaterials without compromising bulk properties. Currently, antimicrobial metallic nanoparticles-based surface coating is prepared by reducing the metallic salt using reducing agent through wet chemistry process. This process is time consuming and multistep. Hence a greener and efficient method of fabricating antimicrobial metallic nanoparticles coated surfaces will be much appreciated in the current state of biomedical research. In the present work, we report a simple green plasma-based method of producing copper and silver nanoparticles coated polymer surfaces by reducing the metallic salts (Ag⁺¹, Cu²⁺) with low temperature hydrogen plasma treatment. This reduction process was found to be efficient in producing metallic nanostructures on the surface of hydrophilic cellulose paper surface. The morphology and distribution of the metallic nanostructures formed on cellulose paper surface can be controlled by varying the timing of hydrogen plasma exposure. Such facile method of producing metallic coatings such as Ag, and Cu may be extended to tissue engineered scaffolds which may have potential application in biomedical research.