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. 2019 Feb 14;10(2):123.
doi: 10.3390/mi10020123.

Effect of Process Parameters and Material Properties on Laser Micromachining of Microchannels

Matthew Benton  1 , Mohammad Robiul Hossan  2   3 , Prashanth Reddy Konari  4 , Sanjeewa Gamagedara  5   6
Affiliations

Effect of Process Parameters and Material Properties on Laser Micromachining of Microchannels

Matthew Benton et al. Micromachines (Basel). .

Abstract

Laser micromachining has emerged as a promising technique for mass production of microfluidic devices. However, control and optimization of process parameters, and design of substrate materials are still ongoing challenges for the widespread application of laser micromachining. This article reports a systematic study on the effect of laser system parameters and thermo-physical properties of substrate materials on laser micromachining. Three dimensional transient heat conduction equation with a Gaussian laser heat source was solved using finite element based Multiphysics software COMSOL 5.2a. Large heat convection coefficients were used to consider the rapid phase transition of the material during the laser treatment. The depth of the laser cut was measured by removing material at a pre-set temperature. The grid independent analysis was performed for ensuring the accuracy of the model. The results show that laser power and scanning speed have a strong effect on the channel depth, while the level of focus of the laser beam contributes in determining both the depth and width of the channel. Higher thermal conductivity results deeper in cuts, in contrast the higher specific heat produces shallower channels for a given condition. These findings can help in designing and optimizing process parameters for laser micromachining of microfluidic devices.

Keywords: laser ablation; laser micromachining; laser system parameters; microchannels; microfabrication; modeling of laser micromachining.

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Conflict of interest statement

The authors declare no conflict of interest. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
(a) Schematic of a typical CO2 laser machining setup, where f is the focal length of the focusing lens, and d is the distance between the substrate and the focusing length. (b) Schematic of a polymer slab that is subject to laser ablation. The dimensions (a × b × c) of the slab are parametrically defined based on the size of the laser beam and channel length.
Figure 2
Figure 2
The temperature and depth of cut as measured at t = 0.0052 s for different mesh sizes for convergence analysis. Constant material properties and laser system parameters listed in Table 1 and Table 2 were used. (a) T = 700 K Isotherm for different element sizes; (b) Channel depth determined from each mesh.
Figure 3
Figure 3
The laser spot size as a function of the distance between the focal point and the substrate.
Figure 4
Figure 4
(a) Channel depth as a function of laser power for various spot sizes. (b) Shape of the channel cut out by 40% laser power with various laser spot sizes. Spot sizes are varied by considering focused and unfocused beam according to Equation (11).
Figure 5
Figure 5
Effect of laser scanning speed on the laser ablation; (a) the depth of cuts for various laser scanning speed are presented with increasing laser power. (b) Channel depth as a function of laser power for various spot sizes. (b) channel shape for the different scanning speed with 40% of laser power.
Figure 6
Figure 6
Depth vs. laser power for various thermal conductivity values. All material and system properties, other than thermal conductivity, are set to the values found in Table 1 and Table 2.
Figure 7
Figure 7
Channel depth for materials for a range of specific heats in laser ablation as a function of laser power.
Figure 8
Figure 8
Depth vs laser power for various convection coefficients. Variation in the depth of cuts is observed for the higher convective coefficient.
See this image and copyright information in PMC

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