Plasma–surface interaction at atmospheric pressure: A case study of           polystyrene etching and surface modification by Ar/O<sub>2</sub> plasma           jet

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Treatments of polymer films using either a MHz atmospheric pressure plasma jet (APPJ) or an atmospheric pressure surface micro-discharge (SMD) plasma are investigated. While the typical approach to determine relevant reactive species is to correlate surface effects with gas phase species measurement, this does not capture potential synergistic or other complex effects that may be occurring. Activation energy and directionality of the etching process can characterize what is occurring at the surface for these processes in more detail. The APPJ source shows an apparent activation energy of ∼0.18 eV at 8 mm distance and up to ∼0.34 eV at 16 mm distance for a temperature range of 20-80°C tested with thin polymer films. The APPJ source shows directional etching at 8 mm distance with less anisotropy the more distance is increased. The SMD source has an apparent activation energy of ∼0.8-0.9 eV at a distance of 3 mm. The SMD also only shows isotropic etching behavior. However the SMD surface chemistry changes significantly to less oxidation with increased temperature while the APPJ source induced modifications remain very similar with temperature change. The lower apparent activation energy of the APPJinduced etching reactions as compared with low pressure work (0.5 eV) and observation of line-of-sight contribution to etching suggests the involvement of a directional species at closer distances facilitating the etching which falls off with increasing distance. The high activation energy of the SMD suggests that species with less capability for etching is responsible compared to the APPJ and low pressure plasma. The high surface oxidation from low temperature SMD treatments shows that the surface is being oxidized but not sufficiently to reach the desorption step of the etching process.

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Polymer etching by atmospheric‐pressure plasma jet and surface micro‐discharge sources: Activation energy analysis and etching directionality

Knoll

Luan

Pranda

et al. 2018

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Interaction of long‐lived reactive species from cold atmospheric pressure plasma with polymers: Role of macromolecular structure and deep modification of aromatic polymers

Luan

Oehrlein

2019

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We report (a) the deep modification of polymers by long-lived reactive species generated in atmospheric pressure plasma and (b) the dependence of plasma-polymer interaction on the macromolecular structure. Styrene-based polymers show significant thickness expansion whereas polymers with methyl, alcohol, and ether side groups show low-rate etching. The characterization of polystyrene (PS) by X-ray photoelectron spectroscopy and attenuated total reflectance-Fourier transform infrared shows that plasma treatment destroys aromatic rings and produces ether, ester, and surface organic nitrate groups.These modifications can happen at tens of nanometers below the surface, which we attribute to the reaction-diffusion of plasma species. Comparing three styrene-based polymers namely PS, poly(4methyl styrene), and poly(αmethyl styrene), we find that long-lived species primarily attack the C-H bond on the carbon site where the aromatic ring connects.

Sensitivity of tumor versus normal cell migration and morphology to cold atmospheric plasma‐treated media in varying culture conditions

Pranda

Murugesan

Knoll

et al. 2019

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Cold atmospheric plasma (CAP) produces reactive oxygen species and reactive nitrogen species, which may disproportionally damage tumor cells, resulting in potentially selective cancer therapy. Here, we compare the effects of two CAP sources, that is, the atmospheric pressure plasma jet and the surface micro discharge, on the selectivity of CAP-treated cell-culture media. CAP-treated media were applied to metastatic breast tumor cells and their normal breast epithelial cell counterparts to assess treatment selectivity, while systematically varying common cell-culture media and cell-matrix binding moieties. We show that media compositions are crucial in a CAP-treated media selectivity, while binding moieties (specifically, collagen I, fibronectin, and poly-D-lysine) play a lesser role. These data have further implications in the translation of CAP to in vivo use. K E Y W O R D Scancer, cell culture, cold plasma, selectivity, therapy