scholarly journals Direct Laser Processing of Two-Scale Periodic Structures for Superhydrophobic Surfaces Using a Nanosecond Pulsed Laser

2020 ◽  
Vol 7 (4) ◽  
pp. 496-512 ◽  
Author(s):  
Hidenori Shimada ◽  
Shunichi Kato ◽  
Takumi Watanabe ◽  
Masaki Yamaguchi
Keyword(s):  
Contact Angle ◽  
Laser Processing ◽  
Periodic Structures ◽  
Pulsed Laser ◽  
Processing Method ◽  
Superhydrophobic Surfaces ◽  
Processing Rate ◽  
Nanosecond Pulsed Laser ◽  
Direct Laser ◽  
Micro Holes

AbstractHierarchical structures are promising geometries for superhydrophobic surfaces, however a processing method with a single laser light source that is capable of both one-pass and rapid processing has not been established. The purpose of this study was to propose a concept of direct laser processing of two-scale periodic structures exhibiting superhydrophobicity. We hypothesized that the molten material that occurs due to the expanding plasma and that is squeezed around the micro-holes could play an active role in the processing of two-scale periodic structures. Percussion drilling using a nanosecond pulsed laser (532 nm wavelength) was performed on a steel surface. Twenty four different test-pieces were prepared using pitch (16–120 μm), number of repetition shots (1–120), and fluence (2.49–20 J/cm2), as the parameters. As the results, micro-holes with bank-shaped outer rims were formed. The maximum apparent contact angle was 161.4° and the contact angle hysteresis was 4.2° for a pitch of 80 μm and 20 repetition shots. The calculated results for the apparent contact angles were consistent with the measured results. Finally, an equation for estimating the processing rate was proposed. We demonstrated that this direct processing method can achieve a maximum processing rate of 823 mm2/min.

scholarly journals Product and Process Fingerprint for Nanosecond Pulsed Laser Ablated Superhydrophobic Surface

Micromachines ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 177 ◽  
Author(s):  
Yukui Cai ◽  
Xichun Luo ◽  
Zhanqiang Liu ◽  
Yi Qin ◽  
Wenlong Chang ◽  
...  
Keyword(s):  
Contact Angle ◽  
Laser Ablation ◽  
Process Parameters ◽  
Superhydrophobic Surface ◽  
Surface Characterization ◽  
Pulsed Laser ◽  
Threshold Value ◽  
Machined Surface ◽  
Water Contact ◽  
Nanosecond Pulsed Laser

Superhydrophobic surfaces have attracted extensive attention over the last few decades. It is mainly due to their capabilities of providing several interesting functions, such as self-cleaning, corrosion resistance, anti-icing and drag reduction. Nanosecond pulsed laser ablation is considered as a promising technique to fabricate superhydrophobic structures. Many pieces of research have proved that machined surface morphology has a significant effect on the hydrophobicity of a specimen. However, few quantitative investigations were conducted to identify effective process parameters and surface characterization parameters for laser-ablated microstructures which are sensitive to the hydrophobicity of the microstructured surface. This paper proposed and reveals for the first time, the concepts of process and product fingerprints for laser ablated superhydrophobic surface through experimental investigation and statistical analysis. The results of correlation analysis showed that a newly proposed dimensionless functional parameter in this paper, Rhy, i.e., the average ratio of Rz to Rsm is the most sensitive surface characterization parameter to the water contact angle of the specimen, which can be regarded as the product fingerprint. It also proposes another new process parameter, average laser pulse energy per unit area of the specimen (Is), as the best process fingerprint which can be used to control the product fingerprint Rhy. The threshold value of Rhy and Is are 0.41 and 536 J/mm2 respectively, which help to ensure the superhydrophobicity (contact angle larger than 150°) of the specimen in the laser ablation process. Therefore, the process and product fingerprints overcome the research challenge of the so-called inverse problem in manufacturing as they can be used to determine the required process parameters and surface topography according to the specification of superhydrophobicity.

Holographic laser processing for three-dimensional photonic lattices

2017 ◽  
Author(s):  
Satoru Shoji ◽  
Remo Proietti Zaccaria ◽  
Satoshi Kawata
Keyword(s):  
Lattice Constant ◽  
Laser Processing ◽  
Periodic Structures ◽  
Three Dimensional ◽  
Processing Method ◽  
Direct Writing ◽  
Photosensitive Polymers ◽  
Photonic Lattices ◽  
Lattice Symmetry ◽  
Beam Technique

This article describes a holographic laser-processing method for independently controlling the lattice symmetry and lattice constant in three-dimensional photonic lattices. With this approach, optical periodicity is created in lower dimensions and three-dimensional periodicity is obtained by a combination of several lower-dimensional periodic structures. The proposed holographic laser-processing method is compared with the standard four-beam technique. Examples of experimental demonstration achieved in photosensitive polymers are given. The article also introduces a multiphoton direct-writing technique for creating defect structures in lattices towards production of defect cavity-functionalized photonic crystal devices. It shows that all Bravais lattices can be produced by choosing proper incident vectors of laser beams. The lattice constant of the structure can be changed without distorting its lattice symmetry and lattice elements.

scholarly journals Development of Method Enhanced Laser Ablation Efficiency According to Fine Curvature of the Polymer through the Preliminary Preparation Process Using UV Picosecond Laser

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 959 ◽  
Author(s):  
Seung Sik Ham ◽  
Ho Lee
Keyword(s):  
Laser Processing ◽  
Pulsed Laser ◽  
Picosecond Laser ◽  
Processing Method ◽  
New Method ◽  
Shielding Effect ◽  
Ablation Efficiency ◽  
Preliminary Preparation ◽  
Ultrashort Pulsed Laser ◽  
New Processing

In processes using the ultrashort pulsed laser, the phenomenon that the ablation efficiency is reduced due to the increase of the shielding effect of the generated plume is increasingly caused by the use of the high power and high repetition rate. A new method is needed to prevent a decrease in ablation efficiency in processing using an ultrashort pulsed laser. In this study, the proposed a processing method that can improve the ablation efficiency by providing an efficient escape path of plume, and examine the feasibility of a new processing method. The new method we proposed is a method of laser processing after generating a fine curvature in the polymer as a preliminary preparation. The fine curvature of the polymer produced by the preliminary preparation induces an artificial chimney-like opening along the path of the incident beam during laser processing, thereby enabling the plume to be effectively removed. The experiment for examine the feasibility through a new method was conducted using a 10-picosecond laser of UV wavelength with two optical systems. As a new processing method, when processing with ultrashort pulse laser, it was observed that the ablation efficiency improved.

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