Atmospheric Pressure Plasma Processing of Polymers: Plasma Dynamics and Nanoscale Plasma-Surface Interactions

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Project SummaryAtmospheric Pressure Plasma Processing of Polymers: Plasma Dynamics and Nanoscale Plasma Surface InteractionsThis is a computational research program that investigates fundamentals of atmospheric-pressure plasma (APP) transport and plasma-surface interactions in the context of APP processing of polymers. The goals of this program are an integrated, multi-scale modeling hierarchy, spanning scales of nanometers to centimeters, and its use to determine the limiting plasma transport processes and upside potential of APP processing of high-value materials. These goals are met by developing a comprehensive, 3-dimensional plasma-dynamics model for atmospheric-pressure corona and glow discharges that is capable of investigating complex plasma chemistries; developing 3-d plasma-surface interaction algorithms capable of addressing the nanoscale spatial structures typically found on polymers; adapting feature-profile models (originally developed for semiconductor processing) to address plasma-initiated chemistry on polymer surfaces; and integrating these modules into a centimeter-to-nanometer hierarchy.The use of plasmas to produce desired surface properties of a polymer, such as hydrophobicity or hydrophilicity, is a topic both of current scientific investigation and of commercial interest. There are two pathways to achieve this functionalization: deposition and modification. In plasma deposition, polymeric surfaces with specific characteristics are obtained by depositing materials from a plasma. These processes are usually performed at low pressures in systems not unlike those used for microelectronics fabrication. As a consequence, such processing is usually limited to high-value-added materials, such as for biologically compatible coatings. In plasma modification, a conventionally manufactured inexpensive polymer is treated with a plasma to change its surface properties. These processes are typically conducted at atmospheric pressure using corona discharge devices in a "web" arrangement. Unlike low-pressure plasma deposition, APP (atmospheric pressure plasma) processing of polymers is usually a low-value-added process. Polymers and plastics such as polypropylene and polyethylene are processed to improve their adhesion and wettability. In spite of the commercial use of APPs for treating polymers, there are few first order, fundamentals-based models describing the plasma-surface interactions that modify polymer surfaces. As a consequence, the development and optimization of APPs for polymer processing has been, for all practical purposes, an empirical undertakingBroader Impacts The economic and societal benefits of being able to adapt inexpensive and high-volume APP methods for modifying polymers to produce high-value films is staggering. For example, biocompatible artificial skin for treatment of burn patients could be produced for $1/m2 as opposed to $1,000's to $10,000's per m2 which is typical of newly FDA-approved products. The current knowledge base is inadequate to make these advances and improving that knowledge base will help determine the practicality of achieving these goals. The computational techniques and improvements in the knowledge base produced in this project are applicable to a variety of APP applications, including lighting, toxic gas remediation, sterilization of surfaces, bioremediation, and microdischarges..