Interaction of Photons with Polymers: From Surface Modification to Ablation

Abstract

Summary: This work reviews the interaction of photons with polymers with an emphasis on UV laser ablation and surface modification using VUV lamps. Laser ablation of polymers is an established process in industrial applications, but the mechanisms of ablation are still controversial. Different polymers, such as poly(methyl methacrylate), polyimides and specially designed polymers are used as examples to show that the mechanism is a mixture of photochemical and photothermal features which are closely related to the polymer structure and properties. Different approaches to probe the ablation mechanisms and to improve ablation are discussed. Photoactive groups have been introduced into the polymer structure to improve the quality of ablation and to elucidate the ablation mechanisms. The experimental techniques to probe the ablation mechanism range from time‐resolved measurements, such as shadowgraphy, ToF‐MS, and ns‐surface interferometry to variations of the irradiation wavelengths and pulse lengths. The necessity for a critical evaluation of the experimental procedures and analysis is discussed exemplary for polyimides. The data for different types of polyimides are mixed up and some experimental procedures are possibly causing problems for the data evaluation. Various recent trends for laser ablation, such as ultrafast ablation or VUV ablation are also discussed. Surface modifications of polymers using VUV photons from lamps are discussed for oxidation and nitriding of poly dimethylsiloxane (PDMS) and polyolefines. The mechanism of the PDMS surface oxidation is presented in detail.

Laser Surface Texturing of Polymers for Biomedical Applications

“…More recently, some research works (using in vivo and in vitro tests) have been performed to elucidate this enhancement in the biological response of the laser-treated polymeric biomaterials; however, more studies are still needed to transfer this technique into the current clinical practice. With this work, we intend to complement reviews on laser patterning, mainly concentrated on laser ablation mechanisms (e.g., [21,[25][26][27]), and to provide the reader with a critical understanding on the next steps to advance in this field.…”

Inorganic Polyphosphate Modulates TRPM8 Channels

“…Using the approach of Dancshazy and coworkers [210], it is possible to surmise that a single UV quantum should locally heat a 100-unit RNA-like polymer by tens of degrees Celsius. Even if the absorbed energy can be promptly transmitted to a template, local heating of the template can eventually cause ablation of the molecule [211]. In the UV-irradiated environment, both outcomes could lead to polymer deterioration.…”

Ablation of polymers by focused EUV radiation from a table-top laser-produced plasma source

“…For these wavelengths, ablation can be described in terms of thermal, photo-thermal and photo-chemical models, or as a combination of these mechanisms [6]. From a practical point of view, a structuring process based on photochemistry is preferable, since the absence of thermal influences leads to smoother profiles with less debris, accomplishing higher spatial resolu-F. Barkusky ( ) · A. Bayer · K. Mann Laser-Laboratorium-Göttingen e.V., Hans-Adolf-Krebs-Weg 1, 37077 Göttingen, Germany e-mail: frank.barkusky@llg-ev.de tion and smaller structure sizes.…”

“…From a practical point of view, a structuring process based on photochemistry is preferable, since the absence of thermal influences leads to smoother profiles with less debris, accomplishing higher spatial resolu-F. Barkusky ( ) · A. Bayer · K. Mann Laser-Laboratorium-Göttingen e.V., Hans-Adolf-Krebs-Weg 1, 37077 Göttingen, Germany e-mail: frank.barkusky@llg-ev.de tion and smaller structure sizes. A prerequisite for a predominant photochemical process without thermal load is short wavelength radiation with photon energies high enough to directly break the polymer bonds [6]. Furthermore, taking the Rayleigh criterion into account, the use of short wavelength radiation increases the theoretical resolution of optics, accomplishing the direct generation of feature sizes below 100 nm [7].…”