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Scaffold processing
Published in Yoshinobu Onuma, Patrick W.J.C. Serruys, Bioresorbable Scaffolds, 2017
John J. Scanlon, Joseph M. Deitzel, Dieter Mairhörmann, Roland Wölzein
To avoid changes in the mechanical properties of polymer tubes during cutting, scaffolds are produced using a cold laser cutting process that imparts no thermal damage to the polymer. Excessive generation of heat during cutting can reduce the molecular weight and change the crystallinity of the polymer. To minimize heat generation, ultra-short pulse lasers are employed. Ultra-short pulse lasers have pulses in the range of 300–800 femtoseconds and wavelengths ranging from about 500–1100 nm. As a general rule, lasers can cut features about 10–15 wavelengths in size. Therefore, a laser has the capability of easily cutting a precise strut pattern in a tube having strut width less than 100 microns.
Application of Graphene in Lasers
Published in Qiaoliang Bao, Hui Ying Hoh, Yupeng Zhang, Graphene Photonics, Optoelectronics, and Plasmonics, 2017
Yao Chen, Haoran Mu, Yupeng Zhang, Qiaoliang Bao
Q-switching and mode-locking are mainly two methods to realize ultrashort pulse laser. Q-switching could generate output pulse with width in the ms and ns, which has the characteristics of high- pulse energy. The mode-locking technology can generate ps pulse and fs pulse as well as higher peak power. To achieve Q-switching and mode-locking, both active and passive methods are available. Relatively, passive mode-locking and passive Q-switching methods do not need an electric field or light field modulation; they only need the insertion of nonlinear optical components known as saturable absorbers in the laser cavity, so that it is more convenient and efficient and could be easily realized.
Impact of the Oil Temperature on the Frictional Behavior of Laser-Structured Surfaces
Published in Tribology Transactions, 2019
Andreas Janssen, Mohammad Dadgar, Wolfgang Wietheger
Microstructures can be manufactured on surfaces by various methods. LST or laser structuring is an accurate method for microstructuring that is based on ablation of material by means of laser radiation. Duration of the pulses is important in laser materials processing. The laser used in this work is an ultrashort pulse laser and delivers pulses with a pulse duration of only a few picoseconds. The ultrashort pulse laser process provides a high degree of structural flexibility and precision in terms of manufacturing technology because no melt and heat-affected zone is generated. Although this view is physically not correct, it practically can be assumed as shown in Weikert (15). This enables the surface structures to be produced with less construction time and cost compared to alternative manufacturing processes. Additionally, postprocessing is not necessary when using an ultrashort pulse laser. The characteristics and phenomenology of ultrashort pulse laser ablation and its separation from other forms of laser ablation have been discussed in the literature (Momma, et al. (16); Janssen (17); Nolte (18)).