Precision Micromachining Research Articles

One-pot microfluidic fabrication of micro ceramic particles

In the quest for miniaturization across technical disciplines, microscale ceramic blocks emerge as pivotal components, with performance critically dependent on precise scales and intricate shapes. Sharp-edged ceramic microparticles, applied from micromachining to microelectronics, require innovative fabrication techniques for high-throughput production while maintaining structural complexity and mechanical integrity. This study introduces a “one-pot microfluidic fabrication” system incorporating two device fabrication strategies, “groove & tongue” and sliding assembling, achieving an unprecedented array of microparticles with diverse, complex shapes and refined precision, outperforming traditional methods in production rate and quality. Optimally designed sintering profiles based on derivative thermogravimetry enhance microparticles’ shape retention and structural strength. Compression and scratch tests validate the superiority of microparticles, suggesting their practicability for diverse applications, such as precise micromachining, sophisticated microrobotics and delicate microsurgical tools. This advancement marks a shift in microscale manufacturing, offering a scalable solution to meet the demanding specifications of miniaturized technology components.

Ultrasonic elliptical vibration micro-cutting mechanism of CoCrFeNiAlX short fiber reinforced aluminum-based composite

This study explores the precision micro-machining of CoCrFeNiAlX short fiber-reinforced 7A09 aluminum matrix composites, focusing on the interplay between machining parameters and composite properties. The investigation scrutinizes the influence of vibrational amplitude, oscillation frequency, penetration depth, fiber orientation, and aluminum concentration on machining dynamics. Findings reveal that enhancing the X-axis vibrational amplitude to 80 μm is associated with a decrease in machining force, which then rises after reaching a threshold. In contrast, maintaining the Y-axis amplitude below 90 μm significantly increases the machining force. Higher amplitudes and frequencies were observed to reduce machining forces by up to 57% at an ultrasonic frequency of 15 kHz. Employing ultrasonically assisted vibration cutting (UEVC) culminated in a substantial 72% decrease in machining forces when fibers were optimally oriented at 45°. The study also identifies a direct correlation between the cutting temperature and both the vibrational amplitude and penetration depth, with the Y-axis amplitude having a more significant impact, causing a 55% variation in temperature. An increase in frequency initially lowers the cutting temperature, with the lowest temperature of 92 °C achieved at 5 kHz, while the peak temperature occurs at a machining depth of 60 μm. Temperature profiles indicate an initial rise with increased fiber orientation, followed by a decline. A slight increase in aluminum concentration marginally raises the cutting temperature. Furthermore, UEVC is found to produce a parabolic residual stress distribution, where amplitude and penetration depth determine the peak stress levels, and higher frequencies contribute to stress reduction. Fiber orientation also affects residual stress, with proper alignment reducing compressive stress and misalignment increasing it. The lowest point of residual compressive stress is detected in the Al0.6 fiber composite, while the peak is observed in the Al1 composites.

Wavelength selection for femtosecond laser processing of materials: Comparison of ablation efficiency and surface quality

We investigated the effects of the femtosecond laser wavelengths λ = 1035, 515, and 345 nm on the laser ablation of 64FeNi alloy (Invar). The ablation rate and ablation efficiency for the three wavelengths were obtained through material-removal experiments of stationary irradiation and laser scanning, respectively. Among laser–matter interaction parameters, the effective penetration depth (α−1) and ablation threshold fluence (Fth) could be estimated from the experiments and were found to be proportional to λ. The ablation rate and ablation efficiency for the peak fluence range of 0.2 J/cm2 < F0 < 1.0 J/cm2 and F0 > 1.0 J/cm2 were the highest at λ = 515 and 1035 nm, respectively, which could be confirmed by using analytical models with α−1 and Fth. The smoothest (roughest) processed surfaces could be obtained at λ = 345 nm (1035 nm) owing to the shortest (longest) periodicity of laser-induced periodic surface structures. Thus, surface smoothing at λ = 345 nm over a certain ablation depth after ablation at λ = 1035 nm, i.e., double-wavelength ablation, can be used for improving surface quality. These results can help in the selection of the proper λ for implementing precise laser micromachining with high productivity.

Highly stable pulsed fiber laser generation modulated by chromium iodide film

Abstract Highly stable pulsed fiber lasers are key optical components in optical communication, optical sensing, and precision micromachining systems due to the high beam quality, high peak power, and compact configurations. However, the available optical modulators in the fiber laser suffer from the operation bandwidth limitations and poor long-term physicochemical stability. Here, we have investigated the broadband nonlinear optical absorption behavior of the chromium iodide (CrI3) film, which exhibits broadband saturable absorption towards the mid-infrared regime and excellent long-term stability. The conventional soliton fiber laser operating at telecom wavelength has been obtained from an Er3+-doped fiber laser (EDFL) utilizing CrI3 film with a signal-to-noise ratio (SNR) of 92.4 dB and a pulse width of 492 fs. In addition, a passively Q-switched operation around 2.8 μm has also been obtained from an Er3+-doped ZBLAN fiber laser (EDZFL) modulated by the CrI3 film with a SNR of 46.8 dB and a pulse width of 766 ns. The demonstration shows that the CrI3 film exhibits robust broadband optical modulation, and may make inroads for developing highly stable ultrafast optoelectronic devices.

Spark discharges at the interface of water and heptane: emulsification and effect on discharge probability

Spark discharges in liquid have shown great potential for use in numerous applications, such as pollutant degradation, precision micromachining, and nanomaterials production. Herein, spark discharges are initiated at the interface of two immiscible liquids, heptane and water. This leads to the formation of an emulsion via mechanisms akin to bubble dynamics and instabilities at the gas–liquid. At high discharge number, an additional mechanism contributes to emulsion formation, resulting in an increase in the number of smaller heptane droplets in water. Analyses of the current–voltage characteristics show that high probability of discharge occurrence is obtained when the electrodes are aligned with the interface. This result is correlated with the low erosion rate of the electrodes. In the case of discharges at the interface, we observed that beyond a certain number of discharges, the breakdown voltage drops; far from the interface, it increases with the discharge number. Based on 2D simulation with a Monte Carlo approach to consider various droplet distribution in water, the electric field distribution is determined. The results support the fact that the decrease in breakdown voltage may be attributed to the intensification of the E-field in water close the heptane droplet. Therefore, spark discharges generated at the interface of a heptane/water system produce an emulsion of heptane in water, which facilitates the occurrence of subsequent discharges by intensifying the electric field and reducing the breakdown voltage.

The best of two worlds

AbstractFounded in 2013, Femtika is a spinoff company of the Laser Research Center of Vilnius University, Lithuania. The experts there have many years of experience in the research and development of 3D laser precision micromachining, and they specialize in hybrid micromachining technology.

Diffraction-limited high-power master oscillator – power amplifier system oscillating in visible spectral range on copper atomic transitions for precise material micromachining

A new considerably improved master oscillator–power amplifier copper bromide vapor system delivering diffraction-limited high-power laser radiation at the atomic copper 510.6- and 578.2-nm lines is developed and investigated. The highest beam quality achieved so far with laser systems oscillating on the metal self-terminating transitions is confirmed by two independent methods. Precise micromachining is realized on silica, ceramics, silicon, and stainless steel. Though the aspect ratio of the crater drilled in optical grade fused quartz through the wave-guide-assisted method is higher than the one obtained so to date, a new method is also developed to make the aspect ratio almost limitless.

Micromachining of SiO2 single crystal wafer using femtosecond laser

Silicon dioxide (SiO2), a new type of inorganic nonmetallic material, has been widely used in people's livelihood and military industry. For silicon dioxide-based applications, ultra-precision micromachining is a crucial component that impacts the performance of the finished products. This research reports the precise micromachining of silicon dioxide wafers by femtosecond laser. A prediction model for groove processing size is developed, and an experiment is carried out to investigate the silicon dioxide groove processing technology. The effects of processing parameters that include laser power, scanning speed, scanning repetitions, and defocus amount on the processed properties of grooves, the heat affected zone, and processed roughness are discussed. The variable defocus processing method is proposed, which can effectively improve the inclination angle of the groove wall and the quality of the machined groove. Moreover, scanning electron microscopy is used to analyze the groove morphology, allowing for the improvement of surface quality and processing parameter optimization.

Perspective on ultrashort pulse laser micromachining

Ultrashort pulse lasers have found widespread applications in precise micromachining. Here, we present our brief perspective on the development of this innovative technology from the 1990s until today.

Waveguide integration of a &gt;4.7‐THz quantum‐cascade laser

Waveguide integration of terahertz quantum cascade lasers (THz QCLs) is demonstrated at frequencies above 4.7 THz. A precision micromachining technique, followed by diamond-turning and electroless-plating has been used to manufacture hollow rectangular waveguides with integrated diagonal feedhorns. It is shown that surface roughness at the ≈ 1 μ m $\approx {1}\,{\mu }\text{m}$ level is achieved, enabling outcoupling of radiation in the 4.75–5.05 THz band, with a divergence angle of < 5 ∘ ${<5^{\circ }}$ along the plane of the QCLs substrate.

Laser technology for precise material machining applications

AbstractIn recent years, driven by the need for energy conservation and pollution reduction to develop a sustainable society, the building‐integrated photovoltaics (BIPV), centralized photovoltaic power stations and new energy vehicle markets have grown significantly and with that increased the demand for glass that requires more precise micromachining methods.

Influence of B-field on the characteristics of pulsed spark discharges in water

Spark discharges in water have great potential for use in various technological fields, including pollutant degradation, precision micromachining, and nanomaterial production. However, the large-scale application of these discharges is limited by the complexity of the implicated physical and chemical phenomena, which cannot be easily controlled. In this study, we assess the effect of an external B-field on the electrical characteristics of multiple successive discharges, as well as on the erosion of the electrode. In addition to the B = 0 condition, two configurations of the B-field are investigated: B-parallel and B-perpendicular to the electrode axis, both at the magnitude of 125 mT. The obtained results demonstrate that discharge electrical characteristics and electrode erosion are significantly affected by the B-field. Using a W electrode, the highest and lowest discharge currents are measured in the case of B-perpendicular and B = 0, respectively. Meanwhile, the highest erosion volume is obtained in the case of B = 0. To assess the influence of electrode nature and magnetic properties on the discharges, the results obtained using W (paramagnetic) electrodes were compared to those obtained with Ni (ferromagnetic). The comparison shows that the discharge electrical data are tightly distributed when the Ni electrode is utilized, regardless of the B-condition, whereas the data obtained with the W electrode exhibit significant statistical variations in the presence of the B-field. Overall, the data reported herein indicate that the electrical properties of a spark discharge may be varied and controlled by applying an external B-field.

Assessment on the Optimum Performance of a Novel 3 Axes Micro EDM Developed for Commercial Applications

Abstract A low cost three axes commercial microEDM machine has been developed indigenously in order to implement precision micromachining. The developed microEDM consists of various components such as machining chamber, X-Y table, tool feed and tool holder assembly, dielectric circulation system, power supply and automatic driving devices to control the spark gap distance. The setup is capable of performing the 8µm movement in Z-axis.The developed 3 axes machine and the commercial available machine are investigated with the most important process parameters such as Current, Pulse on time and Pulse off time in order to study the Material Removal Rate (MRR) and Tool Wear Rate (TWR). The material chosen for the current research is Stainless Steel 316L, which has high corrosion resistance and the electrode was tungsten 300µm. In most of the experiments, the developed machine has performed with 6.52% higher MRR and 26.10% Lower TWR. This is due to the effective spark gap circuit developed with the use of hall current sensor.The mathematical model of MRR and TWR are obtained by correlating the process parameter using Response Surface Methodology (RSM).The chosen objectives are contradictory in nature, we employ a non-dominated Genetic algorithm to find the optimal process parameters. The developed 3 axes microEDM has yield a 10.14% and 33.12% better performance on optimum maximum MRR and minimum TWR respectively when compared to the commercial machine.

Multi-Characteristics Optimization in Micro-milling of Ti6Al4V Alloy

Nowadays, Ti6Al4V alloy is widely used to fabricate miniaturized prostheses, orthopedic and dental implants. Surface quality is an essential aspect of the implant parts owing to its effect on service life, which could be achieved through a proper selection of precise micromachining parameters. In this research, the mechanical micromachining of Ti6Al4V alloy has been performed, and optimized process parameters are considered for analysis. Surface roughness (Ra) of the machined microchannels, cutting force in the feed direction (Fy), cross-feed direction (Fx), and vibration on the top surface plate along the spindle axis (a z) have been taken as the response variables and were analyzed. The tests were accomplished at various rotational speed (N), feed per tooth (f z), axial depth of cut (a p), and cutter diameter (D) as machining parameters, each at three levels. The significant factors and their levels are identified using analysis of variance (ANOVA) and S/N ratios of response plot. According to the GRA test, N : 15000 rpm, fz : 0.2 µm/tooth, ap : 30 µm, and D : 200 µm are optimal parameters setting for better machinability of Ti6Al4V. ANOVA results indicated that feed rate is the most influential factor for lower cutting forces, surface roughness, and workpiece vibration. Fast Fourier transform (FFT) analysis depicts the stiffness of different micro end-mills significantly affect the machining performance like vibration amplitude during the micro-milling of Ti6Al4V alloy.

Miriding Mutailipu.

"The natural talent I would like to be gifted with is to assemble atoms and units in optimally aligned configurations … I celebrate success by having a quick break and then working harder than ever before …" Find out more about Miriding Mutailipu in his Introducing … Profile.

Micro electric discharge machining (μ-EDM) of polymer nanocomposites modified by graphene nanoplatelets/carbon using rotating electrode tool

The micro-sized hole is highly required in biomedical, electronics, optical, aerospace components that are not feasible by the traditional machining process. This study highlights the precise micromachining on the polymer nanocomposites modified by graphene nanoplatelet (GNP) and carbon fiber. The electric discharge machining (EDM) of polymeric composites is too complicated due to its lower conductivity and abrasive nature. The little concentration of GNP in the epoxy matrix expands the machinability aspect of the polymers. The reinforcing conductive particle is used for the micro EDM (μEDM) of the laminate nanocomposites with a rotating tool electrode. The Taguchi concept-based orthogonal array was used to execute the machining test. The material removal rate (MRR) during the μEDM of the developed laminate nanocomposites was estimated using the sine cosine algorithm. The tests were conducted at three levels of process constraints: voltages, length of the pulses, and weight % of the GNP. The higher value of MRR is obtained at the optimal condition of voltage at three level, length of pulse two level, and weight % of GNP three level. The quality of the machined hole and the surface damages during the machining test were investigated by a field electron scanning electron microscope. The microscopy findings reveal that GNP addition significantly influences the nanocomposite micromachining.

Toward the Enhancement of Critical Performance for Deep-Ultraviolet Frequency-Doubling Crystals Utilizing Covalent Tetrahedra

ConspectusDeep-ultraviolet (deep-UV, λ < 200 nm) coherent light is emerging as an indispensable driving force behind the innovation of optics and materials science. The deep-UV-driven applications range from laser interference photolithography to precise micromachining to futuristic ideas such as space propulsion using remotely controlled positioning lasers. Unlike conventional approaches to obtaining deep-UV light, for instance, synchrotron radiation, direct laser excitation, and gas discharge, nonlinear frequency conversion can be regarded as a more attractive way to endow such resource with high photon energy, high photon flux, and high spectral resolution. Actually, the nonlinear frequency conversion can be efficient only with the use of high-performing frequency-doubling crystals, which should be well-suited to the physics of nonlinear optical process. However, the necessary prerequisites for a practical frequency-doubling crystal are extremely strict, and thus very few crystals can be used to generate the deep-UV light. Faced with this, sustained effort has been expended by chemists and materials scientists toward discovering novel deep-UV frequency-doubling crystals. Studies have so far indicated that the main difficulty in finding a perfect candidate comes from the combination of three critical properties (absorption edge, nonlinear optical coefficients, and birefringence) into one crystal because they share the mutual relation of restriction and influence.In this Account, we present recent progress in discovering emergent deep-UV frequency-doubling crystals with the discussion of our efforts to balance the three critical properties by introducing the covalent tetrahedra [MO4–nXn] (n = 1–3), in which M refers to central atoms such as B, P, Si, S, Al, Zn, and Be and X can be apical atoms such as F, Cl, Br, and N. By analyzing the influence of the covalent tetrahedra on optical properties, we came to the conclusion of how to use the oxidized tetrahedra to achieve the improvement of the absorption edge, nonlinear optical coefficients, and birefringence for deep-UV frequency-doubling crystals. The followings are the key points in achieving the above goals: (i) elimination of dangling bonds with covalent tetrahedra to push the absorption edge of crystals into the deep-UV spectral region; (ii) orbital hybridization enhancement, charge-transfer energy reduction, and symmetry breaking of original tetrahedra with the introduction of X atoms and thereby the achievement of the enhancement of nonlinear optical coefficients; and (iii) uniform alignment of tetrahedral distorted units and the introduction of polarized X atoms containing [MO4–nXn] tetrahedra with high polarizability anisotropy to cause the large enhancement of birefringence. These findings allow us to understand the microcosmic behaviors of covalent tetrahedra on pushing the current limitations and provide an optional functional group toward the maximum thresholds of three critical parameters for deep-UV frequency-doubling crystals. Finally, we conclude this Account with a better understanding of the positive roles of covalent tetrahedra in enhancing the optical performance and how they can facilitate the construction of high-performing deep-UV crystals.

Micromachining and Characterisation of Folded Waveguide Structure at 0.22THz

The demand of high-speed wireless communication has increased, which need the data rate to be in the order of Terabyte per second (Tbps) in the near future. Terahertz (THz) band communication is a key wireless communication technology to satisfy this future demand. This would also reduce the spectrum scarcity and capacity limitation of current wireless systems. Microfabricated Folded Waveguide TWTs are the potential compact sources of wide band and high-power terahertz radiation. This study primarily focuses on machining technology for THz waveguide components requiring ultra-high precision micromachining. Rectangular waveguides, especially Folded Waveguides (FW), are even more difficult to manufacture using conventional machining techniques due to their small size and very tight tolerances. The criticalities in micromachining of FW for 0.22 THz have been addressed in this article. Half hard free cutting Brass IS 319-H2 was used as a work material due to its electrical and mechanical properties. Waveguide size of 0.852 × 0.12 mm was machined within ± 3–5 μm linear tolerances, surface roughness in the order of 45 nm Ra, and flatness less than half of wavelength (< λ/2). The split top and bottom blocks of the folded waveguide were aligned by dowel pins which matched within a tolerance of ± 5 μm. The perpendicularity and parallelism were maintained within 5 μm tolerance. This work explored and established the application of micromilling as reasonably suitable for the THz waveguides followed by ultrasonic cleaning as deburring. It also investigated the measured folded waveguide losses which were close to simulated values.

Development and investigations on a hybrid tooling concept for coaxial and concurrent application of electrochemical and laser micromachining processes

In hybrid laser-electrochemical micromachining, both laser and electrochemical process energies act along the same machining axis and thus both influence material removal by their interaction. The traditional nozzle based laser assisted jet-ECM concepts require laser to be focused on workpiece surface in an electrochemical environment and are limited in aspect ratios as the nozzle stays above the workpiece surface. In this work, a hybrid tooling concept is proposed for a novel process scheme of precision hybrid laser-electrochemical micromachining. The tool serves the function of both an ECM electrode as well as a leaky-type multimode waveguide for the laser and delivers laser homogeneously together with the electrolyte on the workpiece surface without requiring laser to be focused on the workpiece surface. A precision prototype hybrid machine-tool is developed which employs short pulsed nano-second laser and micro-second pulsed voltage source for precision micromachining. For this system, ray tracing and detailed multiphysics electrochemical micromachining process simulations are carried out to demonstrate the applicability of this hybrid tooling concept and explain the shape evolution. Successful experimental realization of coaxial and concurrent application of electrochemical and laser processes is presented. Prototype tool electrodes are fabricated and experiments are carried out on an in-house developed prototype hybrid machine tool. The results reveal that the proposed hybrid tool is successfully capable of concentrating laser and electrochemical process energies simultaneously in the same machining zone. However, with the initial design of this hybrid tool, a maximum of 30–40% of laser power is available in the machining zone. Some suggestions for further research will be presented.

Pulse to pulse control for highly precise and efficient micromachining with femtosecond lasers.

Micromachining with high repetition rate femtosecond lasers and galvo scanners shows some limitations in the pulses positioning accuracy due to the galvo mirrors acceleration. This is particularly evident during scan speed or direction changes, resulting in a poor quality and overtreatment e.g. in corners. Several scanning approaches have been proposed to tackle these issues like the so-called skywriting (SW) and the pulse-on-demand (POD) being the last limited to ns lasers, moderate pulse repetition rates and scan speeds. Recently, POD approach has been extended to femtosecond laser sources with high power and high repetition rate. Here, for the first time, we explored the huge potential in laser micromachining of femtosecond POD technology associated to a fast galvo scanner. We tested an innovative set-up allowing for precise laser triggering at the requested time and position for MHz repetition rate and scan speed as high as 20 m/s. The pulse position accuracy of the system has been estimated to be ≤ 1µm whilst performances have been evaluated in comparison to conventional scanning and SW. Finally, we report the results of an engraving test on stainless steel. The advantages of the approach we propose are clearly shown in terms of machining quality and precision with respect to conventional scanning and reduction of the processing time by ≈ 40% with respect to SW.