Surface Treatment

Surface Treatment and Modification using TEA CO2 and Excimer Lasers

Surface modification using excimer lasers is a precision technique that alters material surfaces at the micro- or nano-scale while preserving the integrity of the underlying bulk material. These lasers, which emit high-intensity ultraviolet (UV) light through noble gas-halogen mixtures such as argon fluoride (ArF) or krypton chloride (KrCl), offer unique advantages due to their short wavelengths and pulsed operation. The UV photons are absorbed near the surface, enabling controlled ablation with minimal thermal diffusion, which prevents heat-affected zones critical for delicate materials like semiconductors, polymers, and biological tissues. Beyond physical etching or patterning—essential for advanced microelectronics and optics—excimer lasers also induce photochemical reactions to modify surface chemistry, enhancing properties such as biocompatibility, hydrophobicity, or adhesion. This non-contact, versatile process is pivotal in applications ranging from semiconductor manufacturing to medical device engineering, driving innovation in nanotechnology and precision engineering by achieving sub-micron resolution without compromising material quality.

Medical Device Manufacturing

The biomedical industry has embraced excimer and TEA CO2 lasers for their unparalleled precision in modifying surfaces of implantable devices and diagnostic tools. Excimer lasers create carefully controlled micro and nano topographies on titanium implants, enhancing osseointegration by mimicking natural bone structures that promote cellular attachment and proliferation. For polymer-based medical devices such as stents and catheters, these lasers modify surface chemistry without altering bulk properties, improving hemocompatibility and reducing thrombosis risks. TEA CO2 lasers excel in creating microporous structures in biodegradable polymers for controlled drug delivery systems, where pulse duration and energy density can precisely tune pore size and distribution. Both laser types offer the significant advantage of modifying surfaces without introducing chemical contaminants—a critical consideration for materials entering the human body—while simultaneously achieving sterilization through the high-energy ablation process, effectively eliminating potential pathogens from device surfaces.

Polymer Surface Activation

Polymer surface activation represents one of the most commercially significant applications of excimer and TEA CO2 laser technology. These lasers transform relatively inert polymer surfaces into reactive platforms through photochemical and photothermal mechanisms without compromising structural integrity. Excimer lasers break chemical bonds at the surface level, creating free radicals and oxygen-containing functional groups that dramatically increase surface energy and wettability—essential for adhesion in automotive, packaging, and electronics manufacturing. The process creates a nanoscale roughness that enhances mechanical interlocking with adhesives, coatings, and inks. TEA CO2 lasers, with their controlled thermal profile, selectively modify surfaces of heat-sensitive polymers like polyethylene terephthalate (PET) and polypropylene (PP), enabling high-quality printing and metallization processes. Unlike chemical treatments, laser activation produces no waste byproducts, requires no drying time, and can be precisely patterned, making it increasingly favored in sustainable manufacturing where targeted surface modification of specific areas conserves resources and reduces environmental impact.

Nitriding

Lasers are known to be able to roughen, polish and pattern surfaces but they can also be used to enhance the chemical composition of surfaces.  Such is the case with Nitriding.  In this process, and excimer laser is used to rapidly heat a surface that is exposed to a high pressure Nitrogen atmosphere.  The nitrogen reacts with the plasma created by the laser pulse and bonds are formed between the underlying metal and the nitrogen, created harder more durable surface.  Excimer laser nitriding represents an advanced surface modification technique that introduces nitrogen atoms into metallic surfaces to enhance hardness, wear resistance, corrosion resistance, and fatigue properties without affecting the bulk material characteristics. Unlike conventional nitriding methods that require hours or days of processing, excimer laser nitriding can be completed in seconds or minutes with precise spatial control.  Additionally, the technique can operate at atmospheric pressure with appropriate gas shielding, eliminating the need for expensive vacuum equipment and associated maintenance costs. From an environmental perspective, excimer laser nitriding stands out as a clean process that generates no chemical waste or salt bath disposal issues, aligning with modern sustainable manufacturing principles. Perhaps most metallurgically significant is the ability of the rapid quenching process to form metastable phases—non-equilibrium nitride structures with unique properties that cannot be achieved through conventional heat-treatment approaches.

Nitriding Materials and Applications

Excimer laser nitriding demonstrates remarkable versatility across various high-performance materials and critical applications. The technique proves particularly effective for titanium and titanium alloys, where it creates titanium nitride (TiN) layers that significantly enhance surface properties for biomedical implants, aerospace components, and cutting tools, combining excellent biocompatibility with superior wear resistance. When applied to aluminum and aluminum alloys, the process forms aluminum nitride (AlN) layers that dramatically improve wear resistance while maintaining the lightweight characteristics essential for automotive and aerospace applications. Stainless steel components benefit from enhanced corrosion resistance through carefully controlled nitrogen incorporation that maintains the passive oxide layer critical for performance in aggressive environments. Tool steels treated with excimer laser nitriding develop composite surface layers with finely dispersed nitride particles that substantially extend service life in metal-forming and cutting operations. This adaptability across material systems makes excimer laser nitriding an increasingly valuable technique for industries requiring exceptional surface performance without compromising bulk material properties or component geometry.

For more background on these topics see the following research articles

Laurens, P., Sadras, B., Decobert, F., Arefi-Khonsari, F., & Amouroux, J. (1998). "Enhancement of the adhesive bonding properties of PEEK by excimer laser treatment." International Journal of Adhesion and Adhesives, 18(1), 19-27.
Landmark study demonstrating how excimer laser treatment creates oxygen-containing functional groups on polyetheretherketone (PEEK) surfaces, dramatically improving adhesion properties.

Lippert, T., & Dickinson, J. T. (2003). "Chemical and spectroscopic aspects of polymer ablation: Special features and novel directions." Chemical Reviews, 103(2), 453-486.
Comprehensive review of the photochemical mechanisms underlying excimer laser modification of polymer surfaces, with detailed analysis of chemical transformations.

Rytlewski, P., & Żenkiewicz, M. (2009). "Laser-induced surface modification of polystyrene." Applied Surface Science, 256(3), 857-861.
Investigates the relationship between excimer laser fluence and resulting surface chemistry changes in polystyrene, establishing process windows for controlled surface activation.

Mirzadeh, H., Katbab, A. A., & Burford, R. P. (1995). "KrF laser induced surface modification of polyethylene terephthalate as a means to control cell attachment in vitro." Biomaterials, 16(8), 641-648.
Pioneering study on using excimer lasers to modify PET surfaces for biomedical applications, demonstrating control over cell attachment through laser-induced topographical and chemical changes.

Lasagni, A. F., Hendricks, J. L., Shaw, C. M., Yuan, D., Martin, D. C., & Das, S. (2010). "Direct laser interference patterning of poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) (PEDOT-PSS) thin films." Applied Surface Science, 256(6), 1708-1713.
Demonstrates advanced excimer laser patterning techniques for conductive polymers, relevant for flexible electronics and biomedical sensors.

Srinivasan, R., & Mayne-Banton, V. (1982). "Self-developing photoetching of poly(ethylene terephthalate) films by far-ultraviolet excimer laser radiation." Applied Physics Letters, 41(6), 576-578.
Seminal paper establishing the fundamental mechanisms of excimer laser ablation and modification of polymers, cited over 1,000 times.

Knittel, D., & Schollmeyer, E. (1998). "Surface structuring of synthetic fibers by UV laser irradiation, Part I: Phenomenological report." Polymer International, 45(1), 103-109.
Detailed investigation of excimer laser modification of textile fibers, showing how controlled UV irradiation can enhance wettability and dyeability.

Breuer, J., Metev, S., & Sepold, G. (1995). "Selective surface modification of polymers with CO2-laser radiation." Journal of Adhesion Science and Technology, 9(3), 351-363.
Comparative study between CO2 and excimer laser modification of polymers, highlighting the unique advantages of each approach for different polymer systems.

Callewaert, K., Martelé, Y., Breban, L., Naessens, K., Vandaele, P., Baets, R., Geuskens, G., & Schacht, E. (2003). "Excimer laser induced patterning of polymeric surfaces." Applied Surface Science, 208-209, 218-225.
Demonstrates precise spatial control of surface properties through masked excimer laser treatment for applications in microfluidics and biosensors.

Lazare, S., & Benet, P. (1993). "Surface modifications of polymers under irradiation of excimer lasers: Bisphenol-A polycarbonate and polyimide." Journal of Applied Physics, 74(8), 4953-4957.
Investigates the chemical mechanisms of excimer laser-induced surface oxidation in engineering polymers, correlating surface chemistry changes with laser parameters.

Yao, J. H., Zhang, R. Q., Xu, Y., & Chen, J. M. (2020). "Surface nitriding of titanium alloys with a KrF excimer laser: Microstructural evolution and tribological behavior." Surface and Coatings Technology, 385, 125324.  Comprehensive study of excimer laser nitriding mechanisms on Ti-6Al-4V with detailed analysis of microstructural changes and resulting tribological improvements.

Biswas, A., Majumdar, J. D., Chowdhury, S. G., & Manna, I. (2018). "Laser surface nitriding of Ti-6Al-4V for bio-implant application." Metallurgical and Materials Transactions A, 49(7), 3109-3121.
Investigates the formation of biocompatible TiN layers using excimer laser nitriding for medical implants with focus on cell adhesion and proliferation.

Zimmermann, S., Specht, U., Spieß, L., Romanus, H., Krischok, S., Himmerlich, M., & Ihde, J. (2012). "Improved adhesion at titanium surfaces via laser-induced surface oxidation and roughening." Materials Science and Engineering: A, 558, 755-760.
Examines how excimer laser treatment creates controlled surface topographies that enhance adhesion properties on titanium surfaces.

Höche, D., Müller, S., Rapin, G., Shinn, M., Remdt, E., Gubisch, M., & Schaaf, P. (2015). "Marangoni convection during free electron laser nitriding of titanium." Metallurgical and Materials Transactions B, 46(4), 1814-1822.
Examines the fluid dynamics during laser nitriding that influences nitrogen incorporation and distribution, with principles applicable to excimer laser processing.

Schaaf, P. (2002). "Laser nitriding of metals." Progress in Materials Science, 47(1), 1-161.
Comprehensive review article covering the fundamental mechanisms and applications of laser nitriding, including excimer laser approaches.