Liquid-assisted Laser Research Articles

Optimization of Processing Parameters for Water-Jet-Assisted Laser Etching of Polycrystalline Silicon

Liquid-assisted laser technology is used to etch defect-free materials for high-precision electronics and machinery. This study investigates water-jet-assisted laser etching of polysilicon material. The depths and widths of the etched grooves were investigated for different water-jet incident angles and velocities. To select optimal parameters for a composite etching processing, the results of many tests must be compared, and at least one set of good processing parameter combinations must be identified. Herein, the influence of different parameters on the processing results is studied using an orthogonal test method. The results demonstrate that the depths and widths of the processing grooves were nearly identical at water-jet angles of 30°and 60°; however, the 60° incidence conferred a slight advantage over 30° incidence. The section taper, section depth, and surface topography were optimized at a water-jet velocity of 24-m/s, 1.1-ms laser pulse width, 40-Hz frequency, and 180-A current. Under these conditions, the section taper and groove depth were 1.2° and 1.88 mm, respectively. The groove surfaces exhibited no splitting, slagging, or other defects, and no recast layers were visible.

Experimental research on ultrasound-assisted underwater femtosecond laser drilling

AbstractIn order to diminish the occurrence of cavitation bubbles during the liquid-assisted laser machining, ultrasound-assisted underwater femtosecond laser drilling on stainless steel is adopted. This method greatly diminishes the optical disturbance of cavitation bubbles. By investigating and analyzing the effect of laser pulse energy and pulse number on the morphology of the holes, it has been found that ultrasound not only has a remarkable function of forming a hole with clean and flat bottom, but also reduces debris redeposition around the processing area. This method improves the machining quality. Besides, it also improves the depth-to-diameter ratio of the hole about 20%.

Ultrasonic characterization of dry and wet nanosecond laser ablation of solids

Single-shot nanosecond laser ablation of stainless steel and copper surfaces in ambient air and liquid water environment was studied by contact broadband ultrasonics in the important laser intensity range of 6–450 GW/cm2, covering both regimes of surface phase explosion and formation of sub-critical ablative plasma via optical breakdown in the corresponding dense ablative plume. Similar dependences of ablative plasma pressure were obtained for the dry and wet ablation conditions, differing in their ultrasonic pulse amplitudes by the factor ∼5 and in their pulsewidths by the factor of 1.3 (copper) and 1.6 (steel) for the wet ablation because of the dynamic water-confinement effect. Excepting the confinement effect, these results indicate the similar conditions for pressure generation via sub-critical plasma formation both for the air and water environments, enlightening promising applications of laser ablation for liquid-assisted laser peening and generation of nanoparticles in liquids.

Ionic Liquid-Assisted Laser Desorption/Ionization-Mass Spectrometry: Matrices, Microextraction, and Separation.

Ionic liquids (ILs) have advanced a variety of applications, including matrix-assisted laser desorption/ionization–mass spectrometry (MALDI–MS). ILs can be used as matrices and solvents for analyte extraction and separation prior to analysis using laser desorption/ionization–mass spectrometry (LDI–MS). Most ILs show high stability with negligible sublimation under vacuum, provide high ionization efficiency, can be used for qualitative and quantitative analyses with and without internal standards, show high reproducibility, form homogenous spots during sampling, and offer high solvation efficiency for a wide range of analytes. Ionic liquids can be used as solvents and pseudo-stationary phases for extraction and separation of a wide range of analytes, including proteins, peptides, lipids, carbohydrates, pathogenic bacteria, and small molecules. This review article summarizes the recent advances of ILs applications using MALDI–MS. The applications of ILs as matrices, solvents, and pseudo-stationary phases, are also reviewed.

Liquid-Assisted Femtosecond Laser Precision-Machining of Silica.

We report a systematical study on the liquid assisted femtosecond laser machining of quartz plate in water and under different etching solutions. The ablation features in liquid showed a better structuring quality and improved resolution with 1/3~1/2 smaller features as compared with those made in air. It has been demonstrated that laser induced periodic structures are present to a lesser extent when laser processed in water solutions. The redistribution of oxygen revealed a strong surface modification, which is related to the etching selectivity of laser irradiated regions. Laser ablation in KOH and HF solution showed very different morphology, which relates to the evolution of laser induced plasma on the formation of micro/nano-features in liquid. This work extends laser precision fabrication of hard materials. The mechanism of strong absorption in the regions with permittivity (epsilon) near zero is discussed.

Micromachining of optical fiber its fabrication technologies of liquid-assisted femtosecond laser

ABSTRACTFemtosecond (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.

Experiment and analytical model of laser milling process in soluble oil

The liquid-assisted laser machining process is a promising method to cut materials with minimum thermal damage caused by laser, and water is typically used in the process due to its high thermal conductivity, nontoxicity, and relatively low price. However, water can intrinsically oxidize ferrous metals and in turn deteriorate the workpiece through corrosion during laser ablation in water. This study has for the first time proposed laser ablation in soluble oil to effectively cut the ferrous metals by using laser in a high cooling rate and low potentiality of corrosion to the metals. A nanosecond pulse laser was used to scan over the AISI H13 steel sheet to create a square cavity, while the workpiece surface was covered by a thin and flowing soluble oil film throughout the laser milling process. The effects of laser scan overlap, traverse speed, and liquid flow rate on cavity dimensions and milled surface morphology were experimentally examined. The results revealed that a clean and uniform cavity with a smooth machined surface can be attained by using 70% scan overlap, 6 mm/s traverse speed, and 3.9 cm3/s soluble oil flow rate. Furthermore, analytical models based on heat transfer equations were formulated to predict the cavity profile and cooling of molten droplets in flowing liquid. The predicted profile was found to correspond well to the experiment, and the calculated temperature of cut particles can endorse the experimental findings on debris deposition and recast formation. The implications of this study could bring a new technological approach for damage-free fabrication and fine-scale manufacturing.

Enhanced protein identification using graphite-modified MALDI plates for offline LC-MALDI-MS/MS bottom-up proteomics

The use of offline liquid chromatography-matrix assisted laser desorption/ionization (LC-MALDI) tandem mass spectrometry (MS/MS) for bottom-up proteomics offers advantages in terms of cost, ease of use, and the time-decoupled nature of the separation step and the mass analysis. A method was developed to improve the capabilities of LC-MALDI-MS/MS in terms of protein identification in a bottom-up proteomic workflow. Enhanced protein identification is achieved by an increase in the MALDI signal intensity of the precursor peptides brought about by coating the MALDI plate with a thin film of graphite powder. Using the Escherichia coli proteome, it is demonstrated that the graphite-modified MALDI plates used in an offline LC-MALDI-MS/MS bottom-up protocol led to a 50–135% increase in the number of peptide identifications, and a concomitant 21%–105% increase in the number of proteins inferred. We identify factors that lead to improvements in peptide sequence identifications and in the number of unique proteins identified when compared to using an unmodified MALDI plate. These improvements are achieved using a low cost approach that it is easy to implement, requires no hardware/protocol modification, it is compatible with LC and adds no additional analysis time.

Finite element analysis and simulation of liquid-assisted laser beam machining process

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.

Investigations on the Influence of Liquid-Assisted Laser Ablation of NiTi Rotating Target to Improve the Formation Efficiency of Spherical Alloyed NiTi Nanoparticles

In this work, the liquid-assisted laser ablation of NiTi rotating target has been used as a promising technique for generating spherical NiTi alloy nanoparticles with higher formation efficiency. Nd: YAG nanosecond laser with three different laser wavelengths (355, 532 and 1064 nm), three different laser fluences (30, 40 and 50 J/cm2) and three different rotational speeds (10 RPM, 20 RPM and 30 RPM) of target has been used to ablate the nitinol (Ni-55%, Ti-45%) target. The influences of different laser parameters (wavelengths and fluences) and different RPMs have been studied on the size, morphology and formation of alloy nanoparticles. It has been observed that the formation efficiency is maximum (39.9 mg/h) for smaller size nanoparticle (~40 nm) at 355 nm wavelength, 50 J/cm2 fluence and 10 RPM rotational speed. On the other hand, we find that the formation efficiency (10.5 mg/h) is lowest with a bigger size of nanoparticle (~110 nm) at 1064 nm wavelength, 50 J/cm2 fluence and 30 RPM speed. Therefore, this is a promising technique to synthesize spherical alloy nanoparticles with higher ablation efficiency. Thus, the higher ablation of particles helps to improve the optical absorption of the colloidal solution as optical absorption has a direct relation with the particle concentration. The shape and size of particles were characterized through SEM and DLS analysis whereas the crystallinity was confirmed through TEM and XRD analysis, respectively. Moreover, the elemental analysis was done with the help of XPS and EDS and optical absorption through UV–Vis spectrum analysis.

Evolution of milled cavity in the multiple laser scans of titanium alloy under a flowing water layer

The needs for damage-free and fine-scale features with good surface finish have been challenging today’s manufacturing technologies. Laser machining process performed under a flowing water layer is a capable technique to satisfy these requirements with high processing rate and clean cut surface. However, the capability and performance of this process for milling applications have not clearly been understood yet. Therefore, this study aims at enabling an insight into the laser milling process under a flowing water layer. Titanium alloy (Ti-6Al-4V) was employed as a work sample in this study, and a nanosecond pulse laser was used to ablate the material in water. The effects of laser traverse speed and number of scans on geometrical dimensions, surface and subsurface characteristics were experimentally investigated. The results revealed that a deeper milled cavity with a smaller taper angle was achievable by using a slower traverse speed and more number of laser scans. A trade-off between the uniformity and roughness of milled surface was also evidenced under the different laser traverse speeds examined in this study. By comparing to the laser milling of titanium alloy in ambient air, there was no metallurgical change remarkably found in the laser-milled area when the process was carried out in water. In addition, specific energy required to fabricate a laser-milled cavity was about 18 kWs/mm3 for a single scan technique and linearly increased with the number of scans. The findings of this study will advance the understanding of laser ablation in flowing water as well as other liquid-assisted laser machining techniques. The implication of this study will further open wider applications of liquid-assisted laser ablation for a more intricate micro-fabrication with high resolution, high processing rate, and less thermal damage.

Special regime of liquid-assisted laser ablation of ceramics

Results of experimental study the peculiarities of liquid-assisted laser ablation of alumina–silicate ceramics are reported giving attention particularly to effect of thin-wall glass macrosphere appearance at the end of irradiation onto a formed hole in bulk material. Typical times of formation, size and temperature dynamics, and chemical composition were determined; kinetics and mechanism of formation are discussed in presented paper.

Parametric investigations on the influence of nano-second Nd3+:YAG laser wavelength and fluence in synthesizing NiTi nano-particles using liquid assisted laser ablation technique

This paper investigates the influence of laser wavelengths and laser fluences on the size and quality of the NiTi nanoparticles, generated through underwater solid state Nd:YAG laser ablation technique. The experiments were performed on Ni55%–Ti45% sheet to synthesize NiTi nano-particles at three different wavelengths (1064nm, 532nm and 355nm) with varying laser fluences ranging from 20 to 40J/cm2. Synthesized NiTi nano-particles were characterized through SEM, DLS, XRD, FT-IR, TEM and UV–vis spectrum. It was observed that, maximum particle size of 140nm and minimum particle size of 10nm were generated at varying laser wavelengths. The crystallinity and lattice spacing of NiTi alloy nanoparticles were confirmed from the XRD analysis and TEM images, respectively.

Liquid-assisted laser ablation of advanced ceramics and glass-ceramic materials

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 1064nm 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.

Differentially expressed urinary biomarkers in children with idiopathic nephrotic syndrome.

We performed a discovery phase of urinary proteomic profile in children with idiopathic nephrotic syndrome and validated selected biomarkers. Urinary proteomic profile was performed using isobaric tags for relative and absolute quantitation labeling, coupled with liquid chromatography-matrix assisted laser desorption and ionization analysis. Validation of biomarkers apolipoprotein A1, alpha 2 macroglobulin, orosomucoid 2, retinol binding protein 4 and leucine-rich alpha 2-glycoprotein 1 was done by enzyme-linked immunosorbent assay. Apolipoprotein A1 levels of <0.48 µg/mg of creatinine-differentiated steroid-resistant nephrotic syndrome (SRNS) from first episode nephrotic syndrome, area under curve (AUC) [0.99 (CI 0.9-1.0), 100 % sensitivity and 100 % specificity] and a value of <0.24 µg/mg of creatinine could differentiate SRNS from frequently relapsing nephrotic syndrome/steroid dependent nephrotic syndrome [AUC 0.99 (CI 0.9-1.0), 100 % sensitivity and 100 % specificity]. Alpha 2 macroglobulin could differentiate children with SRNS-focal segmental glomerulosclerosis (FSGS) from SRNS-minimal change disease (MCD) at values >3.3 µg/mg of creatinine [AUC 0.84 (CI 0.62-1.0), 90 % sensitivity and 85 % specificity]. Orosomucoid 2 >1.81 µg/mg of creatinine could distinguish SRNS-FSGS from SRNS-MCD [AUC 0.84 (CI 0.62-1.0), sensitivity 90 % and specificity 85.5 %]. RBP 4 value of >1.54 µg/mg of creatinine differentiated SRNS-FSGS from SRNS-MCD [AUC 0.87 (CI 0.68-1.0), sensitivity 90 % and specificity 85.7 %]. Lower level of apolipoprotein A1 in urine is suggestive of SRNS. Alpha 2 macroglobulin, retinol binding protein 4 and orosomucoid 2 are markers associated with FSGS, with alpha 2 macroglobulin being most predictive.

A sleep-inducing peptide from the venom of the Indian cone snail Conus araneosus

The marine snail Conus araneosus has unusual significance due to its confined distribution to coastal regions of southeast India and Sri Lanka. Due to its relative scarceness, this species has been poorly studied. In this work, we characterized the venom of C. araneosus to identify new venom peptides. We identified 14 novel compounds. We determined amino acid sequences from chemically-modified and unmodified crude venom using liquid chromatography-electrospray ionization mass spectrometry and matrix assisted laser desorption ionization time-of-flight mass spectrometry. Ten sequences showed six Cys residues arranged in a pattern that is most commonly associated with the M-superfamily of conotoxins. Four other sequences had four Cys residues in a pattern that is most commonly associated with the T-superfamily of conotoxins. The post-translationally modified residue (pyroglutamate) was determined at the N-terminus of two sequences, ar3h and ar3i respectively. In addition, two sequences, ar3g and ar3h were C-terminally amidated. At a dose of 2 nmol, peptide ar3j elicited sleep when injected intraperitoneally into mice. To our knowledge, this is the first report of a peptide from a molluscivorous cone snail with sleep-inducing effects in mice. The novel peptides characterized herein extend the repertoire of unique peptides derived from cone snails and may add value to the therapeutic promise of conotoxins.

Laser micro-milling under a thin and flowing water layer: A new concept of liquid-assisted laser machining process

This study proposes a new laser micro-milling technique for minimizing the thermal damage and gaining a higher material removal rate than using the laser alone. A low-pressure waterjet was used to impinge on the workpiece surface in order to form a thin water film, where the laser ablation was made underneath the water layer created. According to the findings, the presented technique can introduce a great reduction in heat-affected zone and significantly increase the cavity depth compared to the other laser milling processes. Experimental analyses and potential use of this new machining technique were also given and discussed.

WITHDRAWN: Laser micro-milling under a thin and flowing water layer: A new concept of liquid-assisted laser machining process

WITHDRAWN: Laser micro-milling under a thin and flowing water layer: A new concept of liquid-assisted laser machining process

Laser Ablation of PMMA in Air, Water, and Ethanol Environments

Liquid-assisted laser ablation technique has become an alternative method to reduce the thermal damage of work material induced by a laser. In this study, water and ethanol were employed as the liquid to aid the laser grooving of polymethyl methacrylate (PMMA) sheet. The whole workpiece was submerged in the liquid and ablated under the different laser powers. A clean and deep groove can be fabricated when the PMMA was machined in the ethanol, while the ablation in water can introduce the smallest heat-affected zone compared to the air and ethanol environments. To realize the laser grooving performance, the ablation models were also developed for the first time in this study.

Visualization of liquid-assisted hard tissue ablation with a pulsed CO2 laser

To investigate the characteristics of liquid-mediated hard tissue ablation induced by a pulsed CO2 laser with a wavelength of 10.6 μm, a high speed camera was used to monitor the interaction between water, tissue and laser irradiation. The results showed that laser irradiation can directly impact on tissue through a vapor channel formed by the leading part of the laser pulse. The ablation debris plays a key role in liquid-assisted laser ablation, having the ability to keep the vapor channel open to extend actuation time. The runoff effect induced by vortex convection liquid flow can remove the tissue that obstructs the effect of the next laser pulse.