Laser Etching Technique Research Articles

High precision microscale 3D manufacturing of ultralow expansion glass by femtosecond selective laser etching

Due to its exceptional dimensional stability in harsh thermal conditions and excellent mechanical and optical properties, Corning ultralow expansion (ULE®) glass is the material of choice in many high-demanding fields such as aerospace, astronomy, and advanced optics. This material has recently attracted renewed attention with the advent of femtosecond laser technology, with a particular focus on the interaction of ultrafast pulses and the material itself. Phenomena like the formation of self-assembled nanogratings and their thermal stability as well as the darkening of laser-affected zones have then been characterized. This paper presents how to exploit femtosecond selective laser etching (SLE) techniques to manufacture truly three-dimensional components. To demonstrate the micrometer-scale accuracy and repeatability of this process from the mm- to the cm-size range, various devices are designed and fabricated: fiber hole arrays with different hole densities, sizes, orientations, and shapes; and fiber V-groove arrays. Additionally, a mechanical flexural fiber mount is presented as an example of how multiple functionalities can be monolithically integrated into a single piece of glass through SLE technology. An example of a passive alignment substrate for optical components is also shown. SLE technique represents a new advancement in the field of microscale manufacturing, enabling the scalable production of custom-designed ULE® glass structures with unprecedented precision and complexity, paving the way for the miniaturized integration of highly stable components.

Comparison of Shear Bond Strength of Orthodontic Brackets Bonded to Enamel Prepared by Er: Yag Laser and Conventional Acid Etching Technique-An in-Vitro Study

Background: Brackets are one of the important components in orthodontic treatment which helps in transferring forces to the teeth to appreciate teeth movement. So, it is very important to have a better bond strength between brackets and teeth which can be achieved by different materials and techniques. Initially, etching (surface preparation) was done on the surface of the teeth by acid (37% phosphoric acid) to bond brackets directly to the teeth. Later with the introduction of lasers, surface preparation was done using Er: YAG laser which was considered as an alternative and better technique when compared with the conventional acid technique. Objective: To compare the differences in shear bond strength of orthodontic brackets bonded to enamel prepared by Er: Yag laser and conventional acid etching technique. Results: The shear bond strength of the acid group showed the least bond strength. ARI Index shows that group 3 laser etched group had major bond failure at favorable site with most number of score value between score1 to 3. ARI Index of group A & B showed most number of score value between score4 to 5 with major bond failure at unfavorable site. Conclusion: ANOVA and Chi-square test revealed statistically significant difference between 3 different groups on assessing the SBS and ARI Index. Group C (laser etched group at W. 1mJ & 10Hz) showed better bond strength at a clinically acceptable level and also had major bond failure at favorable site which produces least damage to the enamel surface. Group B laser etched group even though had higher bond strength of 15.95 MPa, their value highly deviates from the clinically required level of 8Mpa.

Simple and Rapid Method of Microwell Array Fabrication for Drug Testing on 3D Cancer Spheroids.

Three-dimensional (3D) cell culture systems are becoming increasingly popular due to their ability to mimic the complex process of angiogenesis in cancer, providing more accurate and physiologically relevant data than traditional two-dimensional (2D) cell culture systems. Microwell systems are particularly useful in this context as they provide a microenvironment that more closely resembles the in vivo environment than traditional microwells. Poly(ethylene glycol) (PEG) microwells are particularly advantageous due to their bio-inertness and the ability to tailor their material characteristics depending on the PEG molecular weight. Although there are several methods available for microwell fabrication, most of them are time-consuming and expensive. The current study utilizes a low-cost laser etching technique on poly(methyl methacrylate) materials followed by molding with PDMS to produce microwells. The optimal conditions for making concave microwells are an engraving parameter speed of 600 mm/s, power of 20%, and a design diameter of the microwell of 0.4 mm. The artificial tumor achieved its full size after 7 days of cell growth in a microwell system, and the cells developed drugs through a live/dead assay test. The results of the drug testing revealed that the IC50 value of zerumbone-loaded liposomes in HepG2 was 4.53 pM, which is greater than the IC50 value of zerumbone. The HepG2 cancer sphere's 3D platform for medication testing revealed that zerumbone-loaded liposomes were very effective at high doses. These findings generally imply that zerumbone-loaded liposomes have the capacity to target the liver and maintain medication delivery.

The Effects of Etchant on via Hole Taper Angle and Selectivity in Selective Laser Etching.

This research focuses on the manufacturing of a glass interposer that has gone through glass via (TGV) connection holes. Glass has unique properties that make it suitable for 3D integrated circuit (IC) interposers, which include low permittivity, high transparency, and adjustable thermal expansion coefficient. To date, various studies have suggested numerous techniques to generate holes in glass. In this study, we adopt the selective laser etching (SLE) technique. SLE consists of two processes: local modification via an ultrashort pulsed laser and chemical etching. In our previous study, we found that the process speed can be enhanced by changing the local modification method. For further enhancement in the process speed, in this study, we focus on the chemical etching process. In particular, we try to find a proper etchant for TGV formation. Here, four different etchants (HF, KOH, NaOH, and NH4F) are compared in order to improve the etching speed. For a quantitative comparison, we adopt the concept of selectivity. The results show that NH4F has the highest selectivity; therefore, we can tentatively claim that it is a promising candidate etchant for generating TGV. In addition, we also observe a taper angle variation according to the etchant used. The results show that the taper angle of the hole is dependent on the concentration of the etchant as well as the etchant itself. These results may be applicable to various industrial fields that aim to adjust the taper angle of holes.

Path-dependent hydrogen evolution reaction via selective etching of bilayer MoS2 catalysts

Innovative laser etching techniques precisely modulate the density of active sites on the basal plane of bilayer MoS2 and thereby significantly enhance its hydrogen evolution reaction.

MICROTENSILE BOND STRENGTH OF UNIVERSAL ADHESIVE TO DENTIN AFTER ER: YAG LASER PRETREATMENT WITH DIFFERENT CONDITIONING MODES - AN IN VITRO STUDY

Adhesion to dentin remains challenging due to its complex nature that prevents complete infiltration of hydrophobic monomer to hydrophilic dentinal substrate. Recently, Er:YAG laser has been used in dentin pretreatment to enhance the bond strength. A deficient hybrid layer is formed following laser etching as it causes thermal damage and collagen denaturation of dentinal substrate. As the results are controversial, attempts are made to modify laser etching technique with respect to energy density, pulse duration and water spray. Thus, the present study aimed to evaluate the influence of Er:YAG laser conditioning of dentin by activation of Chlorhexidine collagen stabilising agent on the bond strength. Samples included 60 freshly extracted premolar which were divided into three groups (n=20) based on the protocol of dentin pretreatment done: Group 1 (Control) - Phosphoric acid etching followed by universal adhesive; Group 2 (Experimental) - Conventional Er:YAG laser dentioning; Group3 (Experimental) - Er:YAG laser dentin conditioning with coronal reservoir of 0.12% Chlorhexidine. Occlusal class 1 cavity was prepared on the samples followed by which dentin conditioning protocol was carried out for the respective groups. Universal adhesive was applied followed by Composite resin restoration. 1000 cycles of Thermocycling was done and the samples were sectioned to obtain microsections. Microtensile bond strength values were obtained by subjecting the specimens to Universal testing machine.Highest microtensile bond strength value was obtained for group 1 followed by group 3 with least value obtained for Group2 with statistically significant values between the groups. (p<0.0001). Within the limitations of the present invitro study, it can be concluded that preetching with phosphoric acid increases the bond strength of universal adhesive to dentin. Laser conditioning of dentin through activation of chlorhexidine provided better bond strength value of universal adhesive when compared to conventional laser dentin conditioning.

Near-infrared light-responsive functionalised surfaces with shape memory microstructure for droplet manipulation and anti-icing/de-icing

Preparation techniques of functional surfaces by studying the correlations between the macroscopic properties and microscopic morphologies of biological surfaces and by replicating their microstructural features have been widely discussed. However, surfaces with intelligently switched microstructural morphologies, according to the application scenario, have rarely been reported. Herein, laser etching techniques are employed to construct micropillar arrays on a photothermally responsive shape memory polymer (SMP) surface. In situ reversible conversion of surface microstructure morphology is achieved with near-infrared (NIR) light and external forces, further promoting surface wettability conversion. Cycling experiments show that this reversible wettability transition can be repeated many times, demonstrating its applicability as a microdroplet manipulation platform for droplet capture and remote release. By combining the microstructural morphologies and photothermal response properties of the reversible surface transition, the passive anti-icing and active de-icing performance characteristics of different surfaces at various stages are compared by analysing the droplet phase transition processes and variations in ice shear strengths. These functionalized surfaces with NIR light-controlled reversible wettability may allow new possibilities for droplet selection and transfer processes, chemical microreactions and full-process dynamic anti-icing/de-icing applications.

Engineering Catalytically Active Sites by Sculpting Artificial Edges on MoS2 Basal Plane for Dinitrogen Reduction at a Low Overpotential.

Engineering catalytically active sites have been a challenge so far and often relies on optimization of synthesis routes, which can at most provide quantitative enhancement of active facets, however, cannot provide control over choosing orientation, geometry and spatial distribution of the active sites. Artificially sculpting catalytically active sites via laser-etching technique can provide a new prospect in this field and offer a new species of nanocatalyst for achieving superior selectivity and attaining maximum yield via absolute control over defining their location and geometry of every active site at a nanoscale precision. In this work, a controlled protocol of artificial surface engineering is shown by focused laser irradiation on pristine MoS2 flakes, which are confirmed as catalytic sites by electrodeposition of AuNPs. The preferential Au deposited catalytic sites are found to be electrochemically active for nitrogen adsorption and its subsequent reduction due to the S-vacancies rather than Mo-vacancy, as advocated by DFT analysis. The catalytic performance of Au-NR/MoS2 shows a high yield rate of ammonia (11.43×10-8 mol s-1 cm-2 ) at a potential as low as -0.1V versus RHE and a notable Faradaic efficiency of 13.79% during the electrochemical nitrogen reduction in 0.1m HCl.

Combined Femtosecond Laser Glass Microprocessing for Liver-on-Chip Device Fabrication.

Nowadays, lab-on-chip (LOC) devices are attracting more and more attention since they show vast prospects for various biomedical applications. Usually, an LOC is a small device that serves a single laboratory function. LOCs show massive potential for organ-on-chip (OOC) device manufacturing since they could allow for research on the avoidance of various diseases or the avoidance of drug testing on animals or humans. However, this technology is still under development. The dominant technique for the fabrication of such devices is molding, which is very attractive and efficient for mass production, but has many drawbacks for prototyping. This article suggests a femtosecond laser microprocessing technique for the prototyping of an OOC-type device-a liver-on-chip. We demonstrate the production of liver-on-chip devices out of glass by using femtosecond laser-based selective laser etching (SLE) and laser welding techniques. The fabricated device was tested with HepG2(GS) liver cancer cells. During the test, HepG2(GS) cells proliferated in the chip, thus showing the potential of the suggested technique for further OOC development.

Microporous vertically aligned CNT nanocomposites with tunable properties for use in flexible heat sinks

Effective thermal management of electronic systems depends on the heat transfer efficiency or the heat dissipation capability, and the thermal conductivity of heat sink components, which has a critical impact on the performance of the devices. The rapidly growing field of microelectronics creates an enormous need for next-generation flexible, lightweight heat sinks. In this work, flexible, microporous nanocomposites are fabricated utilizing a unique yet easily tunable processing method, targeting heat-sink applications. The highly porous and low-density nanohybrid structures were fabricated in a unique processing technique using conformally pyrolytic carbon (PyC) coated vertically aligned carbon nanotube (VACNT) arrays and polydimethylsiloxane (PDMS) infiltration. Simply by varying the concentration of the PDMS in the VACNT structure, the microporosity can be tuned from 50% to 93%, and at the same time, the density of the structure varies from 0.11 g/cm 3 to 0.51 g/cm 3 . The through-thickness thermal conductivity of the VACNT – PDMS nanocomposites did not vary substantially with increasing PDMS concentration, and the highest performance samples exhibited 14.1 W/mK thermal conductivity. The highly flexible nanocomposite structure also showed excellent mechanical resiliency and exhibited complete recovery from 80% compressive strain. The final heat-sink structure with fins was fabricated by a controlled laser etching technique. Analysis of the flexible VACNT array heat sink showed a significant ∼27% reduction in thermal resistance with an air velocity of 1.5 m/s, and about ∼40% improvement in the output performance of a thermoelectric generator (TEG) on which it was mounted. The high thermal conductivity of VACNTs and the large surface area provided by the microporous structure, as well as the laser-etched fins all together contributed to better thermal management performance.

Rapid preparation of CuO composite graphene for portable electrochemical sensing of sulfites based on laser etching technique

Sulfite (SO32-) is mostly used as a preservative in food products, and excessive human intake can lead to cardiac and cerebral discomfort and other adverse effects. Considering the high cost of existing SO32- detection methods and the complexity of sample handling, this study is based on laser-induced graphene technology and the simultaneous preparation of multisite copper oxide (CuO) nanoparticles and their attachment to the graphene surface, which can help to fully contact with SO32-, so as to develop a highly sensitive and consistent screen-printed electrode as an electrochemical sensor (CuO/rGO/SPE). A portable electrochemical workstation and a specially designed snap-in interface are then used for portable detection of SO32-. The structure and composition of CuO were determined by scanning electron microscopy (SEM) and X-ray diffraction (XRD), etc. The electrochemical performance of the CuO/rGO/SPE sensor was evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The linear response range of the electrode was 1–300 μM, the electrode sensitivity was 122.3 μAcm−2mM−1, and the detection limit was 0.2425 μM. Therefore, the CuO/rGO/SPE electrode has remarkable selectivity, stability, and reliability.

Superhydrophobic and Self-Cleaning Aluminum via a Rapid and Controlled Process

Superhydrophobic and self-cleaning materials have been an extensive topic of research owing to their corrosion resistance, antifouling, and anti-icing properties. In the past, superhydrophobicity in aluminum has been obtained by a variety of techniques involving etching by sandblasting, chemical etching, boiling in water, etc. followed by treatment with a fluorochemical and organic solution. However, these techniques are not controlled, might not be easy to implement on a large scale, and mostly make use of fluorochemicals, which are risky for human health and the environment. Therefore, there is a need for a rapid and controlled fabrication process that can provide patterned superhydrophobicity without compromising the environment or the human health. Here, a rapid, controlled, and environmentally friendly procedure for fabricating a superhydrophobic and self-cleaning aluminum surface has been developed, achieving a contact angle of 158.06° and a sliding angle of 1.94°. In the two-step process, a rough surface was obtained using the laser etching technique in under 3 min, which resulted in a precisely controlled pattern with a dual-scale roughness on the surface (∼20–30 μm). Finally, a low surface energy was imparted to the surface by treatment with stearic acid where a low concentration of 2 × 10–4 M and no more than 10 s of exposure was found to be sufficient. Unlike various superficially coated materials, this superhydrophobic surface is durable and does not lose its properties after dipping in water for up to 4 days, encountering fine sand or mud, or at extreme surrounding temperatures of −18 to 100 °C. Thus, this rapid and controlled process for obtaining superhydrophobic aluminum potentially can be deployed for large-scale, structural applications.

Surface characterization and secondary electron yield measurement of the Ti-Zr-V films deposited on laser-etched copper

The electron multipacting effect and distributed vacuum profile, induced by the interaction of the particles in vacuum chamber with the surrounding walls, are the significant issues in modern accelerators. Laser-etching the inner surface of the vacuum chambers can effectively eliminate the electron multipacting effect, and depositing the non-evaporable getter (NEG) film on the vacuum chamber walls can provide distributed pumping properties. In the present study, Ti-Zr-V NEG films were prepared by magnetron sputtering technique on laser-etched oxygen-free copper (OFC) with different deposition times. The secondary electron yields (SEY), activation kinetics, and resistance of the samples were evaluated. The results show that although the SEYs of the coated laser-etched samples are higher than those of the uncoated laser-etched sample, the maximum SEY values are still below the threshold of the operation requirements. The Ti-Zr-V film deposited on laser-etched surface exhibits obvious nucleation phenomenon with columnar microstructure and can be activated at 180^∘C. Moreover, the coated laser-etched samples present lower resistance compared with the uncoated laser-etched sample. The combination of the laser-etching technique and the NEG thin film is aim to provide a practical treatment for the vacuum chambers in modern accelerators.

Study of Micro- and Nanopatterned Aluminum Surfaces Using Different Microfabrication Processes for Water Management.

Superhydrophobic surfaces demonstrate extreme water-repellence, promoting drop-wise over film-wise condensation, increasing liquid mobility, and reducing thermal resistance for heat-exchanger applications. Introducing topographic structures can lead to modified surface free energy, as inspired by natural systems like the lotus leaf, potentially allowing coating-free ice- and frost-free surfaces under certain conditions. This work presents a study of coating-free aluminum micro/nanopatterns fabricated using micromilling or laser-etching techniques and the resultant wetting properties. Our review and experiments clarify the roles of line-edge-roughness and microstructural geometry from each microfabrication technique, which manifests in technique-specific nano- to midmicro-scale roughness, producing a hierarchical structure in both cases. For micromilling, line-edge-roughness consists of jagged burrs of 1-8 μm thickness with 10-25 μm periodicity along the microlines with constantly changing height on the order of 1-20 μm. These effects simultaneously raise the water contact angle from 52° (unprocessed aluminum) up to 136° but with strong edge pinning effects. On the other hand, laser-etched surfaces exhibit line-edge-roughness with a microstructure of 3-20 μm width and 5-10 μm in height superimposed with evenly spread spikes of 50-250 nm. This results in a high contact angle (>150°) coupled with a low contact angle hysteresis (<15°), promoting superhydrophobicity on a coating-free aluminum surface. It is also shown that for certain cases, line-edge-roughness is more important for the resultant wetting properties than the structure geometry.

Bioinspired Superhydrophobic Cilia for Droplets Transportation and Microchemical Reaction

AbstractIn nature, fluid manipulation plays a crucial role in the life of organisms, which has attracted great attentions of research and industry. Here, a functional bionic cilia surface is designed via the simple magnetic field assistance and laser etching technique. Multidirectional droplet transportation occurs on superhydrophobic cilia surface, which has good mechanical, physical, and chemical stability. The as‐prepared surface covered with cilia in the superhydrophobic (WCA of 156 ± 2°) and hydrophobic (WCA of 119 ± 3°) area possess different adhesion state, which can be used for multiple chemical reactions as a microreaction platform. Furthermore, bionic cilia surface can be used as a transport tool in the analysis and detection with average transfer speed of 2.3 cm s−1, which provides new opportunities in the development of small analysis equipment. Importantly, magnetically induced bionic cilia surfaces have broad potential applications in developing smart surfaces, droplet control, lab‐on‐a‐chip, etc.

Influence of primary electron incident angle and electron bombardment on the secondary electron yield of laser-treated copper

Electron cloud is a persistent problem in operating modern accelerators. It might be eliminated by reducing the secondary electron yield (SEY), which is a property of the material of vacuum chambers. In the present study, the SEYs of oxygen-free copper samples are dramatically mitigated by grooving their surfaces with a laser-etching technique. Such mitigation is realized by trapping incident primary electrons and their induced secondary electrons in the grooves. The SEYs of the laser-etched samples are dependent on the geometrical characteristics of the grooves and the incident angles of the primary electrons, i.e., reducing the incident angle can lead to a reduction in the SEY. Electron bombardment of the grooved surface with an electron dose of 2 × 10−2 C mm−2 will further reduce its maximum SEY from 1.15 to 0.98, which might be attributed to the formation of Cu2O and graphite-like C—C bonds and the removal of surface contaminants.

Formation mechanism of the nanostructure in laser streaming phenomenon.

Laser streaming is a phenomenon in which liquid streaming is driven directly from the laser through an in situ fabricated nanostructure. In this study, liquid streaming of a gold nanoparticle suspension driven by a pulsed laser was studied using a high-speed camera. The laser streaming formation time, streaming velocity, and relative energy conversion efficiency of laser streaming was measured for different nanoparticle concentrations, focal lens position, laser powers, and laser repetition rates. In addition to the laser intensity, which played a significant role in the formation process of laser streaming, the optical gradient force was found to be an important approach involved in the transport and provision of nanoparticles during the formation of laser streaming. This finding facilitated a better understanding of the formation mechanism of laser streaming and demonstrated the possibilities of a new potential laser etching technique based on nanosecond lasers and nanoparticle suspensions. This result can also expand the application of laser streaming in microfluids and other fields that require lasers to move macroscopic objects at relatively high speeds.

Microfluidic Fabrication Techniques for High-Pressure Testing of Microscale Supercritical CO2 Foam Transport in Fractured Unconventional Reservoirs.

Pressure limitations of many microfluidic platforms have been a significant challenge in microfluidic experimental studies of fractured media. As a result, these platforms have not been fully exploited for direct observation of high-pressure transport in fractures. This work introduces microfluidic platforms that enable direct observation of multiphase flow in devices featuring surrogate permeable media and fractured systems. Such platforms provide a pathway to address important and timely questions such as those related to CO2 capture, utilization and storage. This work provides a detailed description of the fabrication techniques and an experimental setup that may serve to analyze the behavior of supercritical CO2 (scCO2) foam, its structure and stability. Such studies provide important insights regarding enhanced oil recovery processes and the role of hydraulic fractures in resource recovery from unconventional reservoirs. This work presents a comparative study of microfluidic devices developed using two different techniques: photolithography/wet-etching/thermal-bonding versus Selective Laser-induced Etching. Both techniques result in devices that are chemically and physically resistant and tolerant of high pressure and temperature conditions that correspond to subsurface systems of interest. Both techniques provide pathways to high-precision etched microchannels and capable lab-on-chip devices. Photolithography/wet-etching, however, enables fabrication of complex channel networks with complex geometries, which would be a challenging task for laser etching techniques. This work summarizes a step-by-step photolithography, wet-etching and glass thermal-bonding protocol and, presents representative observations of foam transport with relevance to oil recovery from unconventional tight and shale formations. Finally, this work describes the use of a high-resolution monochromatic sensor to observe scCO2 foam behavior where the entirety of the permeable medium is observed simultaneously while preserving the resolution needed to resolve features as small as 10 µm.

Etching and drilling of through-holes in thin glass by means of picosecond Bessel beams

In this paper, we present a laser etching and drilling technique for thin glass materials based on the use of finite-energy pulsed Bessel beams orthogonally impinging on the sample surface. Thanks to the elongated focal zone of the quasi-non-diffractive beam, the laser processing can be performed without scanning the beam position along the thickness of the transparent material sample, but simply moving the sample in the plane orthogonal to the beam. We first present the results of single-shot glass microfabrication performed to identify the optimal laser parameters needed for an efficient internal material ablation. We then describe the micromachining technique used for etching the dielectric material at glass–air interfaces and for generating, without chemical etching, through-holes in thin glasses.

In-Plane Anisotropy of Transport Property in BaTbO3-Doped SmBa2Cu3O y Films

BaTbO 3 (BTbO) is one of artificial pinning center materials and forms thick rectangular nanorods with diameters of ~20 nm when it is doped high. We expected that the rectangular na-norods would produce in-plane anisotropy of flux pinning. In this study, we investigated in-plane anisotropy of transport properties in BTbO-doped SmBa 2 Cu 3 O y (SmBCO) films. SmBCO thin films with various contents of BTbO were fabricated by using a pulsed laser deposition method. To investigate the in-plane anisotropy, the critical current density J c was measured at 77 K, 0-9 T, and Φ = 0 o and 45 o , where Φ was defined as an in-plane angle from the a or b-axes of SmBCO. To fix the direction of current in the films, the micro-bridges were fabricated with different Φ = 0 o and 45 o by using the laser etching technique. As a result, J c at Φ = 0 o was higher than one at Φ = 45 o in the films with BTbO contents of 12.0 and 20.0 vol.% at 77 K and at fields of 5 T or more. The anisotropy of J c in high fields for current directions was possibly explained by the rectangular shape of the BTbO nanorods.