Micromachining Applications Research Articles

Fabrication of Micro Cylindrical Electrode with Flat End Shape and its Application in Electrochemical Micromachining

Electrochemical micromachining (EMM) has become more and more important in micro machining in recent years. Micro electrode as the tool of EMM is an essential cell in the machining process. In this study, micro cylindrical electrode is fabricated by electrochemical etching firstly. Second, the flat end shape forming methods for micro cylindrical electrode is investigated. And then, micro electrodes with flat end shape fabricated above is used in electrochemical micro milling process. Finally, a 3D micro structure with three steps is machined on metallic materials by above micro cylindrical electrode with flat end shape.

All-normal-dispersion passively mode-locked Yb-doped fiber ring laser based on a graphene oxide saturable absorber

We have demonstrated an all-normal-dispersion passively mode-locked Yb-doped fiber laser using a graphene oxide/polyvinyl alcohol (GO–PVA) saturable absorber without surfactant, for the first time to the best of our knowledge. The experimental results show that the pulse duration of the mode-locked lasers varies from 191 ps to 1.68 ns, while the cavity round trip time changes from 24 to 458 ns, through the variation of the cavity length. In addition, the proposed passively mode-locked fiber laser demonstrates a maximum average output power of 539 mW with a laser cavity length of 94 m, and the corresponding single pulse energy reaches 0.429 μJ. The proposed mode-locked fiber lasers with large chirp pulses may find potential applications in fiber chirped pulse amplification systems for micromachining, material processing and diagnostic applications.

Polarization changes in temporal imaging with pulses of random light

We consider polarization changes of randomly fluctuating electromagnetic pulsed light in temporal imaging. The polarization properties of pulses formed by the time lens are formulated in terms of the Stokes parameters. For Gaussian Schell-model pulses we show that the degree and state of polarization of the time-imaged pulse can be tailored in versatile ways, depending on the temporal polarization and coherence of the input pulse and the system parameters. In particular, weakly polarized central region of the pulse may become fully polarized without energy absorption. The results have potential applications in optical communication, micromachining, and light-matter interactions.

Polygon Scanner System for Ultra Short Pulsed Laser Micro-Machining Applications

Abstract Ultra short pulsed lasers have gained acceptance in micro-machining applications and many processes have been developed in the lab. Transferring the technology to the manufacturing floor started few years ago as soon as relatively high average power (> 5W) lasers became available. Now that high repetition rates and average powers of 50 Watt and more are reaching the market, the commercially available galvo based laser scanners systems limit the efficient use of this expensive laser power. We present a novel polygon based scanner system incorporating laser and scanner synchronization enabling writing speeds of 50 m/sec and higher.

Laser prototyping of printed circuit boards

AbstractThis paper describes the application of laser micromachining to rapid prototyping of printed circuit boards (PCB) using nano-second lasers: the solid-state Nd:YAG (532/1064 nm) laser and the Yb:glass fiber laser (1060 nm). Our investigations included tests for various mask types (synthetic lacquer, light-sensitive emulsion and tin). The purpose of these tests was to determine some of the basic parameters such as the resolution of PCB prototyping, speed of processing and quality of PCB mapping with commonly available laser systems. Optimization of process parameters and the proposed conversion algorithm have allowed us to produce circuit boards with a resolution similar to that of the Laser Direct Imaging (LDI) technology.

Optimized fabrication of micropipette using laser micromachining process and application in functional electrical stimulation of muscle tissue

A thin tapered glass micropipette has been widely applied in biomedical application. During the micromachining process of tapered micropipette by P-2000 laser-based micropipette puller, four process parameters affect the shape of the micropipette, and they are Heat, Velocity, Delay and Pull, respectively. Because of the interaction between any two of these factors, it is difficult to find the optimal parameters to meet the requirement of micropipette tip shape. A special micropipette shape for the application of functional electrical simulation is fabricated and optimized by the orthogonal experiments. The micropipette shape is with a tip diameter of [email protected], the change value of the tip diameter located at the length of [email protected] as small as than [email protected] and total length of 6-12mm. The experimental results show that the optimum matching ones in the given values of the discrete parameters are with the Heat setting of 700, the Velocity setting of 45, the Delay setting of 145 and the Pull setting of 225. The results and analysis presented in the manuscript are based on the use and settings of CO2 laser-based micropipette puller (P-2000, Sutter Instrument) and no physical equivalence could be defined for the various settings except the Delay parameter. Then its application for functional electrical stimulation of muscle tissue is introduced and the corresponding experiments are performed.

Applications of Nd:YAG laser micromanufacturing in high temperature gas reactor research

Two innovative applications of Nd:YAG laser micromachining techniques are demonstrated in this publication. Research projects to determine the fission product transport mechanisms in TRISO coated particles necessitate heat treatment studies as well as the manufacturing of a unique sealed system for experimentation at very high temperatures. This article describes firstly the design and creation of an alumina jig designed to contain 500μm diameter ZrO2 spheres intended for annealing experiments at temperatures up to 1600°C. Functional requirements of this jig are the precision positioning of spheres for laser ablation, welding and post weld heat treatment in order to ensure process repeatability and accurate indexing of individual spheres. The design challenges and the performance of the holding device are reported. Secondly the manufacture of a sealing system using laser micromachining is reported. ZrO2 micro plugs isolate the openings of micro-machined cavities to produce a gas-tight seal fit for application in a high temperature environment. The technique is described along with a discussion of the problems experienced during the sealing process. Typical problems experienced were seating dimensions and the relative small size (∼200μm) of these plugs that posed handling challenges. Manufacturing processes for both the tapered seating cavity and the plug are demonstrated. In conclusion, this article demonstrates the application of Nd-YAG micromachining in an innovative way to solve practical research problems.

The threshold intensity measurement in the femtosecond laser ablation by defocusing

The measurement of the ablation threshold intensity (ATI) is essential for an ultra-fast laser micro-machining process. Unlike the widely used Liu's method, the method presented in this paper investigates the laser Affected Volume and demonstrates that, on some part of the boundary of the affected volume, the laser intensity is equal to the ATI. By defocusing, the size and the shape of the single pulse laser affected volume can be detected to measure the ATI. The potential to setup a standard database of the ATI of various materials by simply calibrating the samples with a benchmark material is also discussed. The method is practically useful as an in situ measurement method in femtosecond pulse laser micro-machining applications.

Finite Element Analysis of Various Shapes of Flexures

The flexural bearing is used for micro-machining and precision applications where low displacement is involved. It offers the advantage of almost frictionless, vibration free and maintenance free operation. The bearing element is deformed to provide desire relative motion between the surfaces. They are made up of deformable bodies called flexure. These flexures are to be designed for required displacement. However the analytical procedure for analysis of the flexure is not available. Hence, an alternative approach of using FEA is applied for design of flexure analysis. In this work flexure having different size and shape such as triangular, square, rectangular and elliptical are analyzed. The analysis of all the above shapes with various thicknesses for least axial, maximum radial stiffness and equivalent stresses is made. Later the results have been analyzed to choose optimum design of flexure.

Precise Online Auto-focus System in High Speed Laser Micromachining Applications

Abstract Maintaining constant quality is challenging in laser processes where a small focal point down to few micrometers is necessary, because the beam focus must be kept within the limits of narrow depth of focus in the entire working area. We demonstrated the importance of the focus control in sapphire scribing and silicon surface material removal processes. With an online auto-focus system micromachining was made up to 1000 mm/s processing speed with a precision of ±2 μm. According to the test results, the auto-focus system significantly improved the process quality and reliability and allowed using high processing speeds and large wafer sizes with high precision.

P‐184: Application of Deep Micromachining of Silicon Substrates to Realize a Novel Electrochromic Based Projection Display

AbstractIn this paper, we report on the realization of miniaturized projection displays on silicon substrates using a highly programmable deep reactive ion etching technique. The micro‐machined silicon substrates have been used to incorporate Liionic electro‐chromic solutions. The use of tungsten oxide (WO3) in conjunction with the ITO electrodes, leads to a transparent or opaque interfaces which can be used as a method to distinguish different spots in an image, provided an external light source is exploited. The formation of highly complex three‐dimensional structures is feasible during the deep reactive ion etching of silicon wafers, while desired under‐etching is achieved by controlling the etching parameters. The evolution of cup‐like micro‐mirrors can be carried out at micrometer sizes leading to ultra‐high resolution projection systems. A passive addressing is feasible between the top ITO‐lines placed on a glass substrate and the bottom cavity‐holding substrate. By addressing individual or clusters of pixels one can achieve desired images.

A Rate-Sensitive Plasticity-Based Model for Machining of Face-Centered Cubic Single-Crystals—Part I: Model Development

With the increased application of micromachining, including micromilling and microdrilling, the need to develop accurate models for machining at the microscale has been recognized. In particular, the crystallographic effects that are generally neglected in the macroscale cutting models must be incorporated into the micromachining models. Diamond turning and mechanical nanomanufacturing techniques also require an understanding of crystallographic effects during material removal. This work presents a rate-sensitive plasticity-based machining (RSPM) model that is used to determine the specific energies (and thus forces) for orthogonal cutting of face-centered cubic (fcc) single-crystals. The RSPM model uses kinematics and geometry of orthogonal cutting for an ideally sharp cutting edge. The total power is expressed in terms of the plastic power, which is spent for shearing the material within a finite shear zone, and the friction power, which is spent for overcoming the friction at the rake face. In calculating the shearing power, rate-sensitive plastic behavior of fcc metals is considered. In addition, realistic effects of lattice rotation and strain hardening are included in the model. Subsequently, the total power is minimized within the space of geometrically allowable shear angles to determine the shear angle solution, and associated cutting and thrust specific energies, as a function of cutting plane orientation, cutting direction (with respect to the crystal orientation), rake angle, and the coefficient of friction. The calibration procedure for and the experimental validation of the model are provided in Part II.

Creation of 3D microsculptures in PMMA by multiple angle proton irradiation

In recent years the technique of proton beam writing has established itself as a versatile method for the creation of microstructures in resist materials. While these structures can be almost arbitrary in two dimensions, the creation of genuine 3D structures remains a challenge.At the LIPSION accelerator facility a new approach has been developed which combines aspects of ion beam tomography, so far solely an analysis method, with proton beam writing. Key element is the targeted irradiation from multiple angles in order to obtain a much broader range of 3D microstructures than has hitherto been possible.PMMA columns with a diameter of ∼90μm were used as raw material and placed in an upright position on top of a rotational axis. Using 2.25MeV protons patterns corresponding to the silhouettes of the desired structures were written from two or more directions. In a subsequent step of chemical etching irradiated portions were dissolved, leaving behind the finished 3D sculpture.Various objects have been created. For the demonstration of the method a 70μm high model of the Eiffel tower has been sculpted by irradiation from two angles. Using irradiation from three angles a 40μm wide screw with right-handed thread could be crafted which might find applications in micromachining. Also, a cage structure with a pore size of ca. 20μm was written with the intention to use it as a scaffold for the growth of biological cells.

Etching behaviour of tungsten microtool and its applications in electrochemical micromachining

The aim of the paper is to study the electrochemical micromachining (µECM) tool preparation technique and in particular it investigates the effects of µECM parameters such as applied potential, electrolytic concentration, tool positions on final tool shape and dimensions. During microtool fabrication, tungsten microshafts of 0.38 mm are electrochemically etched to make the desired cylindrical tools with conical tips. Electrolyte concentrations are varied in the range of 0.1–1.4 M for the potential differences of 9 V and 15 V AC. The shape and size of the tools are also determined for each set of experiments. The tools thus fabricated are used to fabricate single–hole micronozzle and multiple–holes micronozzle array. Entrance and exit diameters of micronozzles fabricated are measured by SEM and compared to tool geometry.

Tuning of a superconducting microwave resonator at 77 K using an integrated micromachined silicon vertical actuator

A silicon micromachined actuator is used to tune a high temperature superconducting microwave resonator. The superconducting resonator is only 1.24 mm × 0.66 mm and demonstrates a Q of up to 1078 at 6.3 GHz and at 77 K. A tuning range of 12% is demonstrated with a maximum applied voltage of 40 V. The frequency of the resonator is controlled by the proximity of a silicon tuning probe. The room temperature resistivity of the silicon is measured to be 20 Ω cm; this value drops as the device is cooled, but remains the limiting factor in the quality factor of the device. This proof of principle experiment demonstrates the application of silicon micromachining for tuning of superconducting microwave circuits, which is achieved despite the difficulties presented by differing material properties and thermal constraints when cooling to 77 K.

Study of surfactant-added TMAH for applications in DRIE and wet etching-based micromachining

In this paper, etching anisotropy is evaluated for a number of different crystallographic orientations of silicon in a 0.1 vol% Triton-X-100 added 25 wt% tetramethylammonium hydroxide (TMAH) solution using a silicon hemisphere. The research is primarily aimed at developing advanced applications of wet etching in microelectromechanical systems (MEMS). The etching process is carried out at different temperatures in the range of 61–81 °C. The etching results of silicon hemisphere and different shapes of three-dimensional structures in {1 0 0}- and {1 1 0}-Si surfaces are analyzed. Significantly important anisotropy, different from a traditional etchant (e.g. pure KOH and TMAH), is investigated to extend the applications of the wet etching process in silicon bulk micromachining. The similar etching behavior of exact and vicinal {1 1 0} and {1 1 1} planes in TMAH + Triton is utilized selectively to remove the scalloping from deep reactive-ion etching (DRIE) etched profiles. The direct application of the present research is demonstrated by fabricating a cylindrical lens with highly smooth etched surface finish. The smoothness of a micro-lens at different locations is measured qualitatively by a scanning electron microscope and quantitatively by an atomic force microscope. The present paper provides a simple and effective fabrication method of the silicon micro-lens for optical MEMS applications.

Silicon Micromachining Based on Surfactant-Added Tetramethyl Ammonium Hydroxide: Etching Mechanism and Advanced Applications

This paper presents the mechanism behind the accused macroscopic changes in the etched profiles and etch rates caused by the addition of small amounts of surfactants (e.g., Triton X-100) in typical alkaline etchants (e.g., tetramethylammonium hydroxide or TMAH) for silicon micromachining applications targeting the fabrication of microelectromechanical systems (MEMS). In order to stress the technological importance of the surfactant addition in TMAH, the paper presents an overview of novel fabrication methods for the realization of new fixed and freestanding structures in Si{100} wafers using an inexpensive combination of wet anisotropic etching in pure and surfactant-added TMAH. The fixed structures contain perfectly sharp edges and a smooth etched surface finish. Thermally deposited oxide is used as the material for the freestanding structures. The fixed structures serve as molds for the realization of new structural shapes using poly(dimethylsiloxane) (PDMS).

Droplet Behavior on a Rotating Surface for Atomization-Based Cutting Fluid Application in Micromachining

The droplet behavior on a rotating surface has been studied to better understand the physics underlying atomized cutting fluid application. To this end, microturning experiments are carried out and the cutting performance evaluated for varying cutting fluids and at different droplet speeds. Microturning experiments indicate that a cutting fluid with low surface tension and low viscosity generates lower cutting temperatures, whereas a fluid with low surface tension and high viscosity generates lower cutting forces. Single-droplet impingement experiments are also conducted on a rotating surface using fluids with different surface tension and viscosity values. Upon impact, the droplet shape is observed to be a function of both the droplet speed and the surface speed. The spreading increases with increased surface speed owing to the tangential momentum added by the rotating surface. Spreading is observed to also increase with a decrease in fluid surface tension and does not change with the fluid viscosity. The evaporation rate is observed to increase for a rotating surface owing to convective heat transfer. Low surface tension and low viscosity are observed to increase the evaporation rate. It is concluded that a fluid with low surface tension and low viscosity is an effective coolant of the cutting zone, whereas a fluid with low surface tension and high viscosity is effective for lubrication.

Ultrafast laser written active devices

AbstractDirect‐write optical waveguide device fabrication is probably the most widely studied application of femtosecond laser micromachining in transparent dielectrics at the present time. Devices such as buried waveguides, power splitters, couplers, gratings, optical amplifiers and laser oscillators have all been demonstrated. This paper reviews the application of the femtosecond laser direct‐write technique to the fabrication of active waveguide devices in bulk glass materials.

Laser micromachining for biomedical applications

Laser micromachining is becoming a common method for fabrication of microstructured medical devices. Developments in pulsed laser technology have made it possible to achieve precision machining of sub-micrometer features with minimal damage to the surrounding material. Several aspects of laser micromachining, including machining methods, types of lasers used in micromachining, and laser-material interaction, are discussed in this article. Biomedical applications of laser micromachining are also reviewed. The ablation behavior of silicon was examined as a function of laser energy, aperture, and repetition rate. In vitro studies showed that microscale grooves on silicon substrates may be used to orient human aortic vascular smooth muscle cells. We anticipate that the use of laser micromachining for modifying medical and dental devices will become more significant over the coming years.