Studies on CO2 Laser Micromachining on PMMA to Fabricate Micro Channel for Microfluidic Applications
01 Jan 2015-pp 221-238
TL;DR: In this paper, the impact of process parameters like raster speed, laser power, and print resolution on the performance of micro-channels made in PMMA (Poly methyl metha acrylate) substrates is discussed.
Abstract: Microfluidic devices are highly commonplace in the field of biomedical technology, point of care diagnostics and chemical analysis. The rapid and low cost manufacturing of these devices have always been a challenge. CO2 laser micromachining has played an important role in micro-machining of devices at a scale similar to the microfluidic devices although it renders the machined surfaces with high surface roughness. The chapter reports an initiative to do process optimization of laser micromachining technique for producing smooth machined surfaces in the micro scale devices. The chapter discusses the impact of process parameters like raster speed, laser power, print resolution etc. and its optimization using two target functions of dimensional precision and surface roughness on micro-channels 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 CO2 laser for fabricating the micro-channel on PMMA with dimensional accuracy and good surface quality, Analysis of variance (ANOVA) and regression analysis is conducted. It is found that optimum surface roughness of this process is around 7.1 µm at the optimum value of the process parameters 7.5 mm/s (50 % of maximum machine limit) raster speed, 17.9 W (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 observed for analyzing the amenability of these channels to flow of water like fluids for micro-fluidic applications. The chapter also covers a review of work done by various researchers in which they developed different methodology for successful manufacturing of microfluidic devices by employing CO2 laser micromachining.
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TL;DR: A new “tw” 3D microfluidic mixer fabricated by a laser writing/microfabrication technique that finds application in the manipulation of tiny volumes of liquids that are crucial in diagnostics.
Abstract: This paper proposes a new “twisted” 3D microfluidic mixer fabricated by a laser writing/microfabrication technique. Effective and efficient mixing using the twisted micromixers can be obtained by combining two general chaotic mixing mechanisms: splitting/recombining and chaotic advection. The lamination of mixer units provides the splitting and recombination mechanism when the quadrant of circles is arranged in a two-layered serial arrangement of mixing units. The overall 3D path of the microchannel introduces the advection. An experimental investigation using chemical solutions revealed that these novel 3D passive microfluidic mixers were stable and could be operated at a wide range of flow rates. This micromixer finds application in the manipulation of tiny volumes of liquids that are crucial in diagnostics. The mixing performance was evaluated by dye visualization, and using a pH test that determined the chemical reaction of the solutions. A comparison of the tornado-mixer with this twisted micromixer was made to evaluate the efficiency of mixing. The efficiency of mixing was calculated within the channel by acquiring intensities using ImageJ software. Results suggested that efficient mixing can be obtained when more than 3 units were consecutively placed. The geometry of the device, which has a length of 30 mm, enables the device to be integrated with micro total analysis systems and other lab-on-chip devices.
41 citations
TL;DR: In this paper, a microfluidic cavitation-microstreaming-based cell lysis and DNA extraction method is presented. But the performance is limited by ineffective mass transport due to low Reynolds number.
Abstract: We for the first time present a microfluidic cavitation-microstreaming-based cell lysis and DNA extraction method. Chemical lysis and DNA extraction have been demonstrated in a microfluidic format but the performance is limited by ineffective mass transport due to low Reynolds number. Here we propose to employ cavitation microstreaming for enhancing chemical lysis and magnetic-bead-based dynamic solid phase extraction (dSPE) of DNA. Cavitation microstreaming condition is optimized by exciting a microfluidic chip at its flexural resonance frequency (fr) measured via electrical impedance spectroscopy. Strong circulatory flows around bubbles excited at fr yields vigorous agitation, allowing fast lysis, and DNA extraction and purification. The microfluidic device is rapidly fabricated using CO2-laser machining and solvent-assisted thermal bonding of polycarbonate (∼25 min). Laser cutting conditions are experimentally determined to achieve a clean sidewall for negligible nonspecific binding and minimal burrs for unobstructed bonding. Solvent exposure and thermal bonding conditions are also experimentally determined for a leakage-free device with excellent dimensional integrity. Our method, although not fully optimized, exhibits an excellent DNA extraction performance, compared to a commercial kit and previous microfluidic methods. High extraction efficiency (76.9 %) and purity (A260/A280 = 1.85) are achieved for a relatively short assay time (∼25 min). Notably, DNA from as few as 18 cells is successfully extracted even from a highly diluted cell sample (0.18 cells/μl). PCR and electrophoresis results confirm the excellent quality of the extracted DNA. Considering these notable performances, and straightforward fabrication and operation, we anticipate our DNA extraction method will be widely used in microfluidic nucleic-acid analysis devices.
17 citations
Cites background from "Studies on CO2 Laser Micromachining..."
...Determination of laser-machining parameters A CO2-laser machining is well known for its suitability in providing quick and affordable machining of thermoplastic substrates for microfluidic devices [79]....
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...sought to optimize laser-cutting parameters, namely power (P, %), speed (S, %), and frequency (F, Hz) to minimize these machining artifacts [79]....
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TL;DR: In this paper, the micro-channels of several sizes are fabricated in well-known aerospace nickel alloy (Inconel 718) through laser beam micro-milling.
Abstract: Micro-channels are considered as the integral part of several engineering devices such as micro-channel heat exchangers, micro-coolers, micro-pulsating heat pipes and micro-channels used in gas turbine blades for aerospace applications. In such applications, a fluid flow is required to pass through certain micro-passages such as micro-grooves and micro-channels. The fluid flow characteristics (flow rate, turbulence, pressure drop and fluid dynamics) are mainly established based on the size and accuracy of micro-passages. Variations (oversizing and undersizing) in micro-passage’s geometry directly affect the fluid flow characteristics. In this study, the micro-channels of several sizes are fabricated in well-known aerospace nickel alloy (Inconel 718) through laser beam micro-milling. The variations in geometrical characteristics of different-sized micro-channels are studied under the influences of different parameters of Nd:YAG laser. In order to have a minimum variation in the machined geometries of each size of micro-channel, the multi-objective optimization of laser parameters has been carried out utilizing the response surface methodology approach. The objective was set to achieve the targeted top widths and depths of micro-channels with minimum degree of taperness associated with the micro-channel’s sidewalls. The optimized sets of laser parameters proposed for each size of micro-channel can be used to fabricate the micro-channels in Inconel 718 with minimum amount of geometrical variations.
13 citations
01 May 2020
TL;DR: The surface finish of the microelectromechanical system substrate, particularly the ones that are deployed in chip-based optofluidic systems, is of utmost importance, and the overall surfa... as mentioned in this paper.
Abstract: The surface finish of the microelectromechanical systems substrate, particularly the ones that are deployed in chip-based optofluidic systems, is of utmost importance, and the overall surfa...
10 citations
29 Apr 2019
TL;DR: This chapter presents the modelling and optimization techniques commonly used in engineering applications especially in Laser Micromachining process, and a review of laser micromachine processes parameters optimization was studied.
Abstract: This chapter presents the modelling and optimization techniques commonly used in
engineering applications especially in Laser Micromachining process. Design of Experiment
DOE (Response Surface Method and Taguchi), Artificial Neural Network (ANN), Genetic
Algorithm (GA), and Particle swarm optimization (PSO) and mixed techniques are explained
briefly. Furthermore, a review of laser micromachining processes parameters optimization was
studied. Recent researches which used different approaches for modelling and optimization
was presented.
10 citations
References
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TL;DR: In this paper, the authors have obtained cw laser action on a number of rotational transitions of the vibrational band of C${\mathrm{O}}_{2}$ around 10.4 and 9.4.
Abstract: We have obtained cw laser action on a number of rotational transitions of the ${{\ensuremath{\Sigma}}_{u}}^{+}\ensuremath{-}{{\ensuremath{\Sigma}}_{g}}^{+}$ vibrational band of C${\mathrm{O}}_{2}$ around 10.4 and 9.4\ensuremath{\mu}. The laser wavelengths are identified as the $P$-branch rotational transitions from $P(12)$ to $P(38)$ for the 00\ifmmode^\circ\else\textdegree\fi{}1-10\ifmmode^\circ\else\textdegree\fi{}0 band and from $P(22)$ to $P(34)$ for the 00\ifmmode^\circ\else\textdegree\fi{}1-02\ifmmode^\circ\else\textdegree\fi{}0 band. Strongest laser transition occurs at 10.6324\ensuremath{\mu} (vacuum). A cw power output of about 1 mW has been measured. All these laser transitions can also be made to oscillate under pulsed discharge conditions with a small increase in the peak laser power output. No $R$-branch transitions have been seen to oscillate either under cw or pulsed discharge conditions. The wavelength measurements are in reasonable agreement with earlier measurement of the bands in absorption, but there are slight differences. These are ascribed to possible pressure-dependent frequency shift effects. A study has been made of the time dependence of the laser output under pulsed excitation, and some conclusions about possible excitation processes are given. Theoretical interpretation given earlier for laser action on vibrational-rotational transitions is discussed in a generalized form. The theory is applicable to both the linear polyatomic molecules and the diatomic molecules.
339 citations
TL;DR: In this article, the authors investigated the use of a commercial CO2 laser system for fabrication of microfluidic systems in polymers and presented a straightforward model for the channel depth of microchannels dependent on the fabrication parameters.
Abstract: In this paper, we investigate the use of a commercial CO2 laser system for fabrication of microfluidic systems in polymers. We discuss the cutting process with the laser system and present a straightforward model for the channel depth of microchannels dependent on the fabrication parameters. In particular, we examine the influence of the cutting sequence, the number of cut passes, the laser beam velocity and the laser radiant flux. The model allows the prediction of microchannel depths within a maximum deviation of 8 µm for channels that are up to 210 µm in depths. It was shown that, at constant channel depth, the channel width could be varied by 27% by using different cutting parameters. The optimum cutting sequence for the production of a channel -junction is also presented in the paper. The laser system is shown to be a flexible and rapid tool for the production of polymer microfluidic prototypes.
171 citations
TL;DR: In this paper, the effect of the processing parameters (laser power and cutting velocity) under the quality of the cut for several polymeric materials was evaluated in CO2 laser cutting with prefixed processing parameters.
125 citations
Additional excerpts
...(2008), Heng et al. (2006), Davim et al....
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15 May 2001-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the surface of the bio-material polymethyl methacrylate (PMMA) was treated with CO2, Nd:YAG, excimer and high power diode laser (HPDL) radiation.
Abstract: The surface of the bio-material polymethyl methacrylate (PMMA) was treated with CO2, Nd:YAG, excimer and high power diode laser (HPDL) radiation. The laser radiation was found to effect varying degrees of change to the wettability characteristics of the material depending upon the laser used. It was observed that interaction with CO2, Nd:YAG and HPDL effected very little change to wettability characteristics of the PMMA. In contrast, interaction of the PMMA with excimer laser radiation resulted an increase in a marked improvement in the wettability characteristics. After excimer laser treatment the surface O2 content was found to have increased and the material was seen to be more polar in nature. The work has shown that the wettability characteristics of the PMMA could be controlled and/or modified with laser surface treatment. However, a wavelength dependence of the change of the wetting properties could not be deduced from the findings of this work.
103 citations
TL;DR: In this paper, the effects of laser power and processing speed on the depth, width and surface profiles of microchannels manufactured from polymethyl methacrylate (PMMA) of various molecular weights were investigated.
Abstract: This paper reports an investigation on the effects of laser power and processing speed on the depth, width and surface profiles of microchannels manufactured from polymethyl methacrylate (PMMA) of various molecular weights. The CO2 laser employed has a wavelength of 10.6 µm and a maximum power of 25 W. The power used for channel fabrication varied between 0.275 and 2.5 W and the cutting speed ranged from 7.0 to 64 mm s−1. It is observed that the channel depth varies linearly with an increase in laser power at a particular speed. For a prescribed laser power, the channel depth decreased with an increase in laser speed for all the grades of PMMA. The channel width increased with an increase in laser power but decreased with an increase in speed. There is a decrease in the depth of the microchannels with an increase in the molecular weight of PMMA. Though the width decreases with an increase in molecular weights of PMMA, 96.7 kDa PMMA has a smaller width than 120 kDa PMMA which is due to the formation of bulges on the channel rim. The surface profiles of the microchannels were examined by a scanning electron microscope. It is observed that pore formation increased with an increase in molecular weight.
99 citations
"Studies on CO2 Laser Micromachining..." refers background in this paper
...In earlier work Lawrence et al (2001), Nayak et al (2008),Heng Q.et. al(2006),J. Paulo Davima et. al....
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