Liquid vortexes and flows induced by femtosecond laser ablation in liquid governing formation of circular and crisscross LIPSS
飞秒激光烧蚀引起的液体涡流和流动在液体控制形成圆形和十字形 LIPSS 中的作用
円形および十字形のLIPSSの形成を支配する液体中のフェムト秒レーザーアブレーションによって誘発される液体の渦と流れ
액체에서 펨토초 레이저 절제에 의해 유도된 액체 소용돌이 및 흐름은 원형 및 십자형 LIPSS의 형성을 제어합니다
Vórtices líquidos y flujos inducidos por ablación con láser de femtosegundo en la formación de líquidos que gobiernan LIPSS circulares y entrecruzados
Vortex et écoulements liquides induits par ablation laser femtoseconde dans un liquide régissant la formation de LIPSS circulaires et entrecroisés
Жидкостные вихри и потоки, индуцированные фемтосекундной лазерной абляцией в жидкости, управляющие формированием круглых и крестообразных LIPSS
Dongshi Zhang 张东石 ¹ ², Xinzhuo Li ³, Yao Fu ³, Qinghe Yao 姚清河 ³, Zhuguo Li 李铸国 ¹ ⁴, Koji Sugioka ²
¹ Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
中国 上海 上海交通大学材料科学与工程学院 上海市激光制造与材料改性重点实验室
² RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
³ School of Aeronautics and Astronautics, Sun Yat-sen University, Guangzhou 510275, China
中国 广州 中山大学航空航天学院
⁴ State Key Lab of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
中国 上海 上海交通大学材料科学与工程学院 金属基复合材料国家重点实验室
Orientations of laser induced periodic surface structures (LIPSS) are usually considered to be governed by the laser polarization state. In this work, we unveil that fluid dynamics induced by femtosecond (fs) laser ablation in liquid (fs-LAL) can easily break this polarization restriction to produce irregular circular-LIPSS (CLIPPS) and crisscross-LIPSS (CCLIPSS). Fs laser ablation of silicon in water shows formation of diverse LIPSS depending on ablation conditions.
At a high power of 700 mW (repetition rate of 100 kHz, pulse duration of 457 fs and wavelength of 1045 nm), single/twin CLIPSS are produced at the bottom of macropores of several microns in diameter due to the formation of strong liquid vortexes and occurrence of the vortex shedding effect. Theoretical simulations validate our speculation about the formation of liquid vortex with an ultrahigh static pressure, which can induce the microstructure trenches and cracks at the sidewalls for fs-LAL of Si and tungsten (W) in water, respectively. At a low power of 50 mW, weak liquid vortexes are produced, which only give birth to curved LIPSS in the valleys of grooves.
Consequently, it is deduced that liquid vortex plays a crucial role in the formation of macropores. Mountain-like microstructures induce complex fluid dynamics which can cause the formation of CCLIPSS on them. It is believed that liquid vortexes and fluid dynamics presented in this work open up new possibilities to diversify the morphologies of LIPSS formed by fs-LAL.
