What is Plasma Treatment?

By Ibtisam AbbasiReviewed by Lexie CornerNov 15 2024

Many materials, particularly polymers, play a critical role across industries but often require surface treatment to be suitable for modern applications. Plasma treatment is a well-established technique applied to a wide range of materials. Using ionized gases in the form of plasma, this method enables surface modifications to meet specific requirements.¹

Image Credit: Gorodenkoff/Shutterstock.com

Principles of Plasma Treatment

Plasma, the fourth state of matter, is created by applying electrical energy to a gas, causing ion formation. When an energy source, such as electrical energy or radio waves, transfers energy to gas molecules, electrons gain energy and become free, resulting in positively charged ions within the gas. These electrons and ions have sufficient energy to continue colliding with neutral atoms, leading to further ionization.

Another method of producing plasma involves the adiabatic compression of gas, which generates intense heat energy and leads to ionization.² The ionized particles within plasma are fundamental to surface treatment techniques used in various modern applications.

Different Plasma Types

The two main types of industrial plasma systems are atmospheric plasma and low-pressure plasma systems. For surface modification using low-pressure plasma, a vacuum chamber containing partially ionized gas is used, with the material placed inside the chamber for treatment.

Specialized pumps maintain an appropriate pressure level, allowing the introduction of a process gas that creates plasma for surface treatment. Throughout the process, the chamber replenishes the gas to sustain the desired pressure.³

In contrast, atmospheric plasma treatment systems directly expose the material's surface to partially ionized gas. As the gas converts into plasma, it produces a plasma arc, which is then applied to treat the material's surface.⁴ While this method appears simpler than low-pressure plasma systems, atmospheric plasma treatments are highly effective, easily integrated, and widely used in the aerospace and defense industries.

Applications of Plasma Treatment

Surface Cleaning

Plasma treatment is a highly effective method for surface cleaning, removing contaminants such as organic residues. For cleaning applications in microelectronics and biomaterials, glow discharge plasma cleaning is a well-established technique used for over a century to sterilize biological implants.⁵

Plasma cleaning is also effective for disinfection, eliminating harmful pathogens and contaminants at the microscopic level. Reactive plasma is used in surface cleaning, allowing chemical interactions with the material’s surface to remove microorganisms and dust.⁶

Plasma treatment for cleaning material surfaces involves multiple steps. Initially, active species are generated and then transported to the surface of the material. Once at the surface, these species undergo reactions that effectively remove contaminants. Plasma cleaning not only enhances surface characteristics, such as wettability, but also serves as an essential preliminary step for any significant surface modifications.⁷

Adhesion Improvement

Plasma treatment techniques are widely used to improve adhesion properties. Materials like polymers often have low surface energies and contamination layers, which can hinder adhesion and bonding. Atmospheric plasma treatment, in particular, has been shown to increase the adhesion of polymers significantly—sometimes by up to tenfold.⁸

Cold plasma treatment is also used for modifying wood surfaces, enhancing glue adhesion, and facilitating the deposition of thin polymeric layers on metal surfaces. The ionized particles in plasma provide sufficient energy to break chemical bonds on the material’s surface, which then interact with gas particles to modify the surface layers.⁹

A major application is in microelectronics, where Argon plasma is used to treat the surface of printed circuit boards, enhancing interfacial adhesion and overall bonding performance.¹⁰

Plasma Treatment for Functionalization

Plasma treatments are also applied to impart specific properties to materials for various applications. For example, oxygen plasma can be used to enhance hydrophilicity in carbon-nitrogen (C₃N₄) nanosheets by introducing hydroxylamine groups (N-OH) to their surface.¹¹ Extending the treatment duration has been shown to further improve hydrophilic properties.¹¹

This capability makes plasma treatment particularly valuable in areas like drug delivery systems and the textile industry, where enhanced material efficiency is often required for specific applications.

Plasma Treatment for Thin Film Coatings and Depositions

Plasma-enhanced chemical vapor deposition (PECVD) has been widely used over the past 30 years for depositing transparent optical coatings and films. Plasma treatments are employed to deposit nanocomposite optical coatings, with applications in areas such as optical waveguides.

Plasma treatment not only prepares surfaces for efficient film deposition but also imparts functional properties like thermal stability. A key advantage of plasma treatments is their compatibility with other thin-film deposition methods, significantly enhancing the physicochemical performance of the films.¹²

Recent Progress in Plasma Technology Applications

Plasma technology has recently found applications in the food industry, notably in cold plasma processing for food preservation and shelf-life extension. While initially used for microbial destruction and enzyme inactivation, recent research indicates that cold plasma treatment can also reduce the negative effects of thermal processing, particularly on proteins that are prone to denaturation at high temperatures.

The interaction of cold plasma and its reactive species with amino acid structures leads to functional changes in protein molecules, which can expand their applications to areas such as 3D printing. Thus, cold plasma shows promise as an innovative technology with implications for the future of food and nutrition security.¹³

In summary, plasma treatment is essential for imparting desired properties in industrial applications. The textile, automotive, and electronics industries rely on plasma treatment for material functionalization and adhesion enhancement. Given the recent emphasis on sustainability, and with plasma treatment offering eco-friendly and precise processing, the market for plasma technology is likely to grow substantially in the coming years.

More from AZoM: How atmospheric plasma will revolutionize the semiconductor packaging industry

References and Further Reading

1. Oehr, C. (2003). Plasma surface modification of polymers for biomedical use. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. https://www.sciencedirect.com/science/article/abs/pii/S0168583X03006505?via%3Dihub
2. Conrads, H., et al. (2000). Plasma generation and plasma sources. Plasma sources science and technology. DOI 10.1088/0963-0252/9/4/301
3. Thierry (2023). Atmospheric Plasma vs Low Pressure Plasma. [Online] Thierry. Available at: https://www.thierry-corp.com/plasma-knowledgebase/atmospheric-plasma-vs-low-pressure-plasma [Accessed on November 07, 2024]
4. Tri Star Technologies Inc. (2023). Comparing Atmospheric and Low Pressure Plasma Treatments. [Online] Tri Star Technologies Inc. Available at: https://tri-star-technologies.com/blog/comparing-atmospheric-and-low-pressure-plasma-treatments/ [Accessed on November 07, 2024]
5. Aronsson, B., et al. (1997). Glow discharge plasma treatment for surface cleaning and modification of metallic biomaterials. Journal of Biomedical Materials Research. https://doi.org/10.1002/(SICI)1097-4636(199704)35:1%3C49::AID-JBM6%3E3.0.CO;2-M
6. Davide. (2023). How Plasma Treatment is Used For Disinfection. [Online] SCI Plasma, Plasma and Vacuum Specialists. Available at: https://www.sciplasma.com/post/plasma-treatment-for-disinfection [Accessed on November 07, 2024]
7. Belkind, A., et al. (2015). Plasma cleaning of surfaces. [Online] Vacuum Coating and Technology November. Available at: https://www.researchgate.net/profile/Abraham-Belkind-2/publication/284486745_Plasma_cleaning_of_surfaces/links/565b11a008aefe619b242752/Plasma-cleaning-of-surfaces.pdf
8. Shenton, M., et al. (2001). Adhesion enhancement of polymer surfaces by atmospheric plasma treatment. Journal of Physics D: Applied Physics. https://www.doi.org/10.1088/0022-3727/34/18/307
9. Acda, M., et al. (2012). Effects of plasma modification on adhesion properties of wood. International journal of adhesion and adhesives. https://doi.org/10.1016/j.ijadhadh.2011.10.003
10. Shin, D., et al. (2009). Chemical and Mechanical Analysis of PCB Surface Treated by Argon Plasma to Enhance Interfacial Adhesion. IEEE Transactions on Electronics Packaging Manufacturing. https://www.doi.org/10.1109/TEPM.2009.2029700
11. Bu, X., et al. (2016). Surface modification of C3N4 through oxygen-plasma treatment: a simple way toward excellent hydrophilicity. ACS Applied Materials & Interfaces. https://doi.org/10.1021/acsami.6b10516
12. Martinu, L., et al. (2000). Plasma deposition of optical films and coatings: A review. Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films. https://doi.org/10.1116/1.1314395
13. Kumar, N., et al. (2024). Recent advances in cold plasma technology for modifications of proteins: A comprehensive review. Journal of Agriculture and Food Research. https://doi.org/10.1016/j.jafr.2024.101177

Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.