Dielectric insulators with patterned topographic relief were used in dielectric barrier discharge (DBD) plasmas operating at atmospheric pressure to spatially define the formation of filamentary microdischarges (“plasma streamers”). Precise localization of microdischarge streamers is demonstrated with concomitant treatment patterns on surfaces, enabling localized etching, surface micro-texturing, and chemically and structurally induced wettability modification without the use of lithographic masks on the sample. Proof-of-concept examples include generation of arbitrary streamer patterns (lines, arrays, and letters), anisotropic etching of PMMA films, and spatial patterning of Teflon to be hydrophilic. The approach herein allows user-defined patterning of DBD streamers for subsequent modification and treatment of surfaces (e.g., roughness, wettability, etc.), materials deposition, or etching.

Multifunctional polymer surfaces exhibiting both hydrophilic and hydrophobic functionality were created using self-organized plasma “streamer” microdischarges occurring in atmospheric pressure dielectric barrier discharges (DBD) operating with argon and air. Surface chemistry and wettability change of polymethylmethacrylate (PMMA) were found to spatially correlate with self-organized streamer patterns. Gas atmosphere was found to play a significant role on streamer density, pattern stability, and lateral contrast of plasma-induced physicochemical property changes across the surface. Stable streamer patterns, with each streamer surrounded by a glowlike discharge, were obtained in argon; discharges in air had more transient and chaotic streamers that were surrounded by dark “plasma free”-like zones. Air plasma streamer treatment of PMMA resulted in hybrid hydrophilic/phobic surfaces with water contact angles (WCA) ranging from 30° to 100° (PMMA WCA = 75°), depending on processing conditions and location. WCA and XPS mapping after treatment revealed that surface chemistry is preferentially modified near streamers, and moreover, that streamer exposure in air locally renders the surface more hydrophilic, surrounded by regions that are more hydrophobic. Overall, this work demonstrates that self-organized streamers in DBD plasmas could be used for scalable and localized modification of surfaces.

This talk will highlight our recent work on the development of atmospheric pressure plasma tools and methods to modify the roughness, surface chemistry, and wettability of dielectric, polymer, and textile surfaces. Dielectric barrier discharges (DBD) at both low (60 Hz) and high frequency (10s kHz, pulsed), along with RF (13.56 MHz) microplasma jets, were used to directly create hydrophobic/philic areas and bio-reactive groups (-COOH, -CFx, -NH2) on surfaces for subsequent immobilization of enzymes and bioactive compounds for sensing, environmental threat detection, and chemical agent destruction. The goal of the work is to provide fundamental understanding of how interfacial properties, namely chemical termination and surface area, roughness geometry and length scale, and incorporation of 2D/3D nanostructures, can impart multi-functionality to different material surfaces. The effect of various plasma operating conditions (e.g., streamer density, frequency, gas atmosphere, power) on wettability contrast, roughness, surface chemistry, and enzyme grafting and viability for different model surfaces will be discussed.