Search

Liquid-assisted laser beam machining (LA-LBM) process is used as an alternative to existing laser beam machining (LBM) process to address the problems associated with the extreme heat of the laser. In this research, the thermal effects of laser and hydrodynamics effects of the liquid medium in the LA-LBM process are investigated to understand the complex interactions involved in the material removal during LA-LBM process. The study utilizes the versatile multiscale modeling approach by coupling the molecular and continuum domains. The research investigates the role of the water layer in the LA-LBM process along with the material transformations taking place in the water layer in the vicinity of the machined zone. The results of the study augment our existing knowledge of the complex mechanisms involved in the LA-LBM process. Investigation on cavity depth revealed the increase in material removal with the increase in laser heat. The change in water layer thickness revealed the reduction in the radius of the heat-affected zone while further explaining the nodal temperature distribution profile and electron temperature distribution in the water layer. [ABSTRACT FROM AUTHOR]

A novel liquid-assisted strategy was proposed to fulfill sustainable dual-purpose oil–water separation with super-omniphobic mesh in this study. The liquid-assisted super-omniphobic mesh possesses oil-repellent property and high separation efficiency when applied for both water removing and oil removing oil–water separation. [Display omitted] • A liquid-assisted strategy for dual-purpose oil–water separation was proposed. • The as-prepared mesh exhibits excellent super-omniphobicity. • The strategy endows the mesh with an excellent antifouling ability. • The strategy can be universally applicable for most super-omniphobic meshes. • The oil–water separation efficiency of the liquid-assisted mesh exceeds 99%. Sustainable methods for oil–water separation are highly desirable for industries globally as their significant role in various applications, such as the treatments for industrial wastewater or marine oil leakage, which harms the environment and ecology deeply. However, existing super-hydrophobic/super-oleophilic and super-oleophobic/super-hydrophilic surfaces fail to satisfy the requirement of continuous oil–water separation owing to either affinity to viscous oil or poor water resistance. Novel methods available for sustainable oil–water separation are widely desired. Until now, there has been no research conducted on the application of super-omniphobic meshes for oil–water separation. Herein, a liquid-assisted strategy for dual-purpose oil–water separation with super-omniphobic meshes was proposed. The strategy can be applied for oil–water separation by removing either water or oil with high separation efficiency. Meanwhile, by taking advantage of the anti-liquid property of the super-omniphobic mesh, the existing common problems such as viscous oil contamination and caustic aqueous corrosion could be avoided. Moreover, since this strategy adopts super-omniphobic meshes, oil–water separation using this strategy in a harsh environment can also be guaranteed. Compared with the conventional super-wetting meshes for oil–water separation, the strategy proposed in this work ensures that the separation mesh always maintains super-oleophobicity during the oil–water separation process and is universally applicable to a variety of super-omniphobic meshes. The present novel strategy provides a general guide for dual-purpose oil–water separation and a sustainable method for anti-contamination wastewater treatment, which indicates promising applications. [ABSTRACT FROM AUTHOR]

Laser beam micromachining (LBMM) process is one of the important advanced manufacturing processes which can shape almost all engineering materials with micron scale precision even for complex geometries. LBMM process when performed in air generates high heat flux causing thermal damage and poor surface finish on the substrate material. Liquid-assisted laser beam micromachining is considered as an alternate approach to the traditional laser beam micromachining process performed under air to reduce the thermal damages caused due to high heat of laser. The presence of liquid medium also helps in carrying away the molten material from the machining zone thereby preventing re-deposition. The focus of this research is to understand the effect of critical process parameters involved in liquid-assisted laser beam micromachining using finite element simulation technique. The study revealed that the width (diameter) and depth of the heat-affected zone decreased considerably with water film thickness of 0.50 mm and higher. Further experimentation is used to validate the results of the simulation model. The experimental results closely matched with the predictions of the simulation study. Micromachining performed under thin films of water and ethylene glycol showed better surface finish as compared to machining performed without water. This suggests that the liquid medium occupies the void during material removal due to laser beam and helps reducing the thermal damage. [ABSTRACT FROM AUTHOR]

Femtosecond (fs) laser has the advantages of good beam quality and high precision, which is one of the best methods for processing optical fiber mini-sensors, but residual debris on the surface of the machined fiber structure will affect the sensor performance. In this paper, the laser parameters of laser pulses and translation speed were investigated for the quality of fiber micro-cavities contrast in the air and the water, it was proved the effectiveness of using liquid-assisted to improve the quality of laser micromachining. [ABSTRACT FROM PUBLISHER]

Liquid Assisted Laser Beam Micromachining (LA-LBMM) process is an advanced machining process that can overcome the limitations of traditional laser beam machining processes. This research involves the use of a Molecular Dynamics (MD) simulation technique to investigate the complex and dynamic mechanisms involved in the LA-LBMM process both in static and dynamic mode. The results of the MD simulation are compared with those of Laser Beam Micromachining (LBMM) performed in air. The study revealed that machining during LA-LBMM process showed higher removal compared with LBMM process. The LA-LBMM process in dynamic mode showed lesser material removal compared with the static mode as the flowing water carrying the heat away from the machining zone. Investigation of the material removal mechanism revealed the presence of a thermal blanket and a bubble formation in the LA-LBMM process, aiding in higher material removal. The findings of this study provide further insights to strengthen the knowledge base of laser beam micromachining technology.

In this work, results obtained by laser ablation of advanced ceramics and glass-ceramic materials assisted by liquids are reported. A Q-switched Nd:YAG laser at its fundamental wavelength of 1064 nm with pulse-width in the nanosecond range was used to machine the materials, which were immersed in water and ethylene glycol. Variation in geometrical parameters, morphology, and ablation yields were studied by using the same laser working conditions. It was observed that machined depth and removed volume depended on the thermal, optical, and mechanical features of the processed materials as well as on the properties of the surrounding medium in which the laser processing was carried out. Variation in ablation yields was studied in function of the liquid used to assist the laser process and related to refractive index and viscosity. Material features and working conditions were also related to the obtained results in order to correlate ablation parameters with respect to the hardness of the processed materials. [ABSTRACT FROM AUTHOR]

This work describes optically smooth high quality surface machining on poly methyl methacrylate (PMMA) using simple visible-LIBWE (laser induced back-side wet etching using visible laser, v-LIBWE). Micromachining of polymer such as PMMA usually utilizes CO2 lasers. However, minimal feature smaller than 100 μm is difficult to achieve and that the surface quality is not good. Using ultra-violet (UV) laser direct ablation reduces the minimal feature to be below 20 μm but the surface roughness is also not satisfactory (several μm). Here we demonstrated that high surface quality etching on PMMA was achievable by v-LIBWE using low power nanosecond 532 nm laser. The etching threshold is ~50 J/cm2, which corresponded to ~2 mW at 1 kHz repetition rate. Using pulse repetition rate of 1 kHz, trench depth saturated at about 2 μm. Deeper trench (~ 5 μm) is achievable using 30 kHz repetition rate but the process is not consistent and that discontinued trench was often observed. A perspective on the future development of v-LIEBWE on polymer substrate was given. [ABSTRACT FROM AUTHOR]

We report a comprehensive study of laser-initiated, liquid-assisted colloidal (LILAC) lithography, and illustrate its utility in patterning silicon substrates. The method combines single shot laser irradiation (frequency doubled Ti–sapphire laser, 50 fs pulse duration, 400 nm wavelength) and medium-tuned optical near-field effects around arrays of silica colloidal particles to achieve 3-D surface patterning of silicon. A monolayer (or multilayers) of hexagonal close packed silica colloidal particles act as a mask and offer a route to liquid-tuned optical near field enhancement effects. The resulting patterns are shown to depend on the difference in refractive index of the colloidal particles ( n colloid ) and the liquid ( n liquid ) in which they are immersed. Two different topographies are demonstrated experimentally: (a) arrays of bumps, centred beneath the original colloidal particles, when using liquids with n liquid < n colloid , and (b) a combination of holes, created in the interstices between the colloidal particles, and bumps when using liquids with n liquid > n colloid – and explained with the aid of complementary Mie scattering simulations. The LILAC lithography technique has potential for rapid, large area, organized 3-D patterning of silicon (and related) substrates. [ABSTRACT FROM AUTHOR]

Zerodur is a glass ceramic that has zero thermal expansion coefficient. It has good optical transmission in the visible light range. The zero thermal expansion property of Zerodur makes it an important substrate material for precision optical applications such as astronomical telescope and EUVL (13 nm) lithography. In this work, we demonstrated the crack-free micromachining of Zerodur using visible laser-induced-backside-wet-etching (v-LIBWE). We used eutectic Indium Gallium alloy (In/Ga) as the light absorber for the v-LIBWE process. Spectra of the light emission during the ablation or etching were recorded and compared using the real-time monitoring method. Measuring the intensity of the characteristic emission peaks allow us to determine the etching threshold in a more efficient way. [ABSTRACT FROM AUTHOR]