Effect of Process Parameters and Material Properties on Laser Micromachining of Microchannels (original) (raw)
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Experimental Analysis of Laser Micromachining of Microchannels in Common Microfluidic Substrates
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Laser micromachining technique offers a promising alternative method for rapid production of microfluidic devices. However, the effect of process parameters on the channel geometry and quality of channels on common microfluidic substrates has not been fully understood yet. In this research, we studied the effect of laser system parameters on the microchannel characteristics of Polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA), and microscope glass substrate—three most widely used materials for microchannels. We also conducted a cell adhesion experiment using normal human dermal fibroblasts on laser-machined microchannels on these substrates. A commercial CO2 laser system consisting of a 45W laser tube, circulating water loop within the laser tube and air cooling of the substrate was used for machining microchannels in PDMS, PMMA and glass. Four laser system parameters—speed, power, focal distance, and number of passes were varied to fabricate straight microchannels. The ch...
3D transient thermal modelling of laser microchannel fabrication in lime soda glass
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Laser-fabricated microchannels in glass offer a wide range of bioengineering and telecommunication applications. A 1.5 kW CO2 laser with 10.6 µm wavelength was used in this study to fabricate micorchannels on the surface of soda-lime glass sheets. A thermal model of the process was developed based on transient heat conduction due to a pulsed heat input. The resulting equation predicted the temperature distribution in the regions surrounding the laser focus. Temperature – time curves were drawn from those equations, which were useful in estimating the thermal history in the processed samples. The temperature distribution was also used to predict the channel geometry (based on the vaporisation temperature of glass). Most of the laser power used was consumed in bringing the glass to the vaporisation temperature. The model was able to predict the channel width, depth and surface roughness. These laser-fabricated channel characteristics were measured and compared to the results obtained from the thermal model. The laser power, frequency, pulse width and translation speed were the control parameters in both studies; hence a direct comparison was established between the model and the experimental results.
Development and Modeling of Laser Micromachining Techniques
Laser micromachining has great potential as a MEMS (micro-electromechanical systems) fabrication technique because of its materials flexibility and 3D capabilities. The machining of deep polymer structures with complex, well-defined surface profiles is particularly relevant to micro-fluidics and micro-optics. This paper presents the use of projection ablation methods to fabricate structures and devices aimed at these application areas. A better understanding of the mechanisms of thermodynamics and heat transfer in MEMS is desired to improve the thermal performance of MEMS due to the importance of these physical processes. Ablation rate of the laser depends on temperature, the material properties and accumulation of heat in the work material. In consequence, to control the laser processing, thermal distribution of the sample has to be determined, which can be made by modeling of laser ablation. By using such modeling tool, proper laser parameters can be determined easier and faster. Geometry of the domain under investigation varies during the simulation, because laser pulses remove material from the sample, thermal effects, photochemical and other phenomena still exist and so the modeling of laser ablation is a specialised problem. A two dimensional finite element model is developed in this work for laser ablation of polymers. Model has been further modified for fabrication of curved sufaces utilized in MEMS applications.
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Laser machining is commonly used for fabrication of medical devices with microscale features, including vascular stents, drug delivery devices, and scaffolds for tissue engineering with controlled pore size and porosity. The process can also be used to produce structured scaffolds for controlling cell growth, orientation, and location. Moreover, lasers may be used to fabricate complex channel nets in which cells are subsequently seeded or to pattern channels for microfluidic devices. Traditionally, these micro devices were fabricated using silicon substrates, but recently the use of titanium allowed to produce more robust devices at a reasonable cost. In particular, the high quality surfaces that can be obtained with laser machining reduce the liquid flow turbulence and avoid micro cavities formation, critical for bacteria proliferation. The present research reports the results of an investigation on the process capability of laser ablation to produce micro pockets fabricated on titanium sheet (0.5 mm thick). A first experimental campaign was designed for identifying a set of laser ablation cycles able to realize the micro pockets by changing the process parameters as scanning speed, laser power, q-switch frequency, loop number, and duty cycle. Moreover, a process optimization was executed in order to produce the pockets with a highly flat surface. The results were acquired by a confocal laser scanning microscope (CLSM) to obtain high-resolution images with depth selectivity and were analyzed with statistic methods for the identification of the best parameter configuration.
Nanosecond pulsed laser micromachining of PMMA-based microfluidic channels
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This paper reports an investigation on the effects of nanosecond laser processing parameters on the depth and width of microchannels fabricated from polymethylmethacrylate (PMMA). The Nd:YAG solid-state pulsed laser has a wavelength of 1064 nm and a measured maximum power of 4.15 W. The laser processing parameters are varied in a scanning speed range of 400 to 800 pulses/mm, a pulse frequency range of 5 to 11 Hz, a Q-switch delay time range of 170 to 180 µs. Main effects plots and microchannel images are utilized to identify the effects of the process parameters for improving material removal rate and surface quality simultaneously for laser micromachining of microchannels in PMMA polymer. It is observed that channel width and depth decreased linearly with increasing Q-switch delay time (hence average power) and increased nonlinearly with increasing scanning rate and not much affected by the increase in pulse frequency.
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Laser-assisted micro-machining (LAMM) has emerged as a transformative technology in precision manufacturing, enabling the creation of highly intricate micro-features on various materials. This paper provides a foundational overview of LAMM technology, exploring its fundamentals, methods, and applications. The construction of the LAMM temperature field is examined because it is crucial to improve its efficiency and cost-effectiveness. The study delves into the development of industrial femtosecond laser micromachining systems, explores fabrication techniques using LAMM, and discusses its role in the production of ceramics and semiconductors. Furthermore, it examines the capabilities of LAMM in creating 3D microstructures and explores the materials commonly used in laser micromachining. Overall, this paper gives valuable insights into the possible uses of laser-based micromachining technologies in various domains, such as the semiconductor industry, microfluidics, optics, etc. and emphasises the need for additional research to overcome its limitations and increase efficiency and cost-effectiveness.
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Laser-assisted mechanical micromachining (LAMM) is a micro-cutting method that employs highly localized thermal softening of the material by continuous wave laser irradiation focused in front of a miniature cutting tool. However, since it is a heat-assisted process, it can induce a detrimental heat-affected zone (HAZ) in the part. This paper focuses on characterization and prediction of the HAZ produced in a LAMM-based micro-grooving process. The heat-affected zone generated by laser heating of H-13 mold steel (42 HRC) at different laser scanning speeds is analyzed for changes in microstructure and microhardness. A 3-D transient finite element model for a moving Gaussian laser heat source is developed to predict the temperature distribution in the workpiece material. The model prediction error is found to be in the 5-15% range with most values falling within 10% of the measured temperatures. The predicted temperature distribution is correlated with the HAZ and a critical temperature range (840-890 1C) corresponding to the maximum depth of the HAZ is identified using a combination of metallography, hardness testing, and thermal modeling.
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ABSTRACT As an intense heat source laser has been successfully employed in microwelding of materials for manufacturing various miniature components. A sophisticated mathematical model of laser microwelding is ever demanding since experimental investigation of the same is costly, expensive, and time consuming. Very little work has been reported in literature on material flow behaviour in microwelding process. Hence, present work is focused on three-dimensional finite element modelling of heat transfer and fluid flow in laser microwelding process. The fluid flow behaviour is validated using order-of-magnitude analysis of liquid velocity under various driving forces. Estimation of several dimensionless numbers describes the nature of material flow within small weld pool. Temperature dependent material properties, latent heat of melting and solidification are incorporated in the model. A harmony search-based meta-heuristic algorithm is incorporated to identify most suitable unknown model input parameters. Simulated results have been validated against experimental data adapted from independent literature.
The International Journal of Advanced Manufacturing Technology, 2015
After entering the twenty-first century, there has been an ongoing drift toward miniaturization of discrete products in several areas. One such application is microfluidic device used in biomedical applications. The challenge with the manufacturing of microfluidic devices/biochips is that they often make use of broad range of materials within a single chip, making it difficult to manufacture these devices with conventional photolithographic-based techniques. Laser processing of materials has proved to be an important tool for the development of these devices because of the accuracy, flexibility, and the most important one material independence it offers. In this work, laser direct writing technique is used for the fabrication of microfeatures in AISI 1045 steel for the microfluidic applications. The basic purpose of the research work is to assess the performance of direct laser machining for the development of microfluidic channels by investigating the effects of different process parameters using design of experiments (DOE) and regression modeling analysis. The model is developed with Optimal Design IV in Response surface methodology taking five input parameters including the scan strategy which is mostly overlooked in the past research. Analysis of variance (ANOVA) has been carried out for five performance measures namely width error for rectangular section, width error for semicircular section, taper degree, recast layer, and material removal rate. Multiobjective optimization of these performance variables has been carried out, and it has been shown that optimized solutions are obtained at moderate frequencies, high scan speed, and minimum layer thickness.
Studies on CO2 Laser Micromachining on PMMA to Fabricate Micro Channel for Microfluidic Applications
Topics in Mining, Metallurgy and Materials Engineering, 2015
Microfluidic devices are in great demand in the field of biomedical technology,point of care diagnostics and chemical analysis. The rapid and low cost manufacturing of these devices have been a challenge. CO 2 laser micromachining plays an important role in machining although it renders the machined surfaces with high roughness.This study is an attempt to do process optimization of laser micromachining technique which may produce smooth machined surfaces. Herein, the impact of process parameters like raster speed ,laser power, print resolution etc. are optimized using two target functions ofdimensional precision and surface roughness on microchannels made in PMMA (Poly methyl metha acrylate) substrates. The laser machined PMMA samples are analyzed using 3D-profilometry and Field emission scanning electron microscope (FESEM) for surface quality and dimensional precision.To investigate optimum process parameters of CO 2 laser for fabricating the microchannel on PMMA with dimensional accuracy and good surface quality, Analysis of variance (ANOVA) and regression analyses is conducted. It is found that optimum surface roughness of this process is around7.1µm at theoptimum values of the process parameters 7.5 mm /sec (50% of maximum machine limit)raster speed, 17.9Watt (51% of maximum machine limit) laser power and 1200 DPI (100% of maximum machine limit)printing resolution. The static contact angle of the micro-machined surface has also been observedfor analyzing the amenability of these channels to flow of water like fluids for micro-fluidic applications.