Abstract
Micromodels are ideal candidates for microfluidic transport investigations, and they have been used for many applications, including oil recovery and carbon dioxide storage. Conventional fabrication methods (e.g., photolithography and chemical etching) are beset with many issues, such as multiple wet processing steps and isotropic etching profiles, making them unsuitable to fabricate complex, multi-depth features. Here, we report a simpler approach, femtosecond laser material processing (FLMP), to fabricate a 3D reservoir micromodel featuring 4 different depths—35, 70, 140, and 280 µm, over a large surface area (20 mm × 15 mm) in a borosilicate glass substrate. The dependence of etch depth on major processing parameters of FLMP, i.e., average laser fluence (), and computer numerically controlled (CNC) processing speed (), was studied. A linear etch depth dependence on was determined while a three-phase exponential decay dependence was obtained for . The accuracy of the method was investigated by using the etch depth dependence on relation as a model to predict input parameters required to machine the micromodel. This study shows the capability and robustness of FLMP to machine 3D multi-depth features that will be essential for the development, control, and fabrication of complex microfluidic geometries.
Highlights
The use of micromodels, known as porous media, for microfluidic transport investigations has been extensively studied in the literature for many applications, such as oil recovery [1,2,3,4,5] and carbon dioxide storage [6,7,8,9,10,11] processes
Silicon and glass-based micromodels have been used to study pore-scales to understand oil-water-solid interactions, multiphase flow, and the dynamics of microemulsions in enhanced oil recovery processes [4,5,11,12]. This is due to the ability to fabricate micromodels to mimic the three dimensional, multiple depths naturally occurring in porous media, and the ease to integrate them with optical instruments for real time and in-situ observation of complex flow behaviour [13]
Occurring porous media consist of complex 3D networks of pores and throats that makes them challenging to study with 2D micromodels, as the physics of the third dimension, which are critical for understanding flow in porous media, cannot be captured
Summary
The use of micromodels, known as porous media, for microfluidic transport investigations has been extensively studied in the literature for many applications, such as oil recovery [1,2,3,4,5] and carbon dioxide storage [6,7,8,9,10,11] processes. With FLMP, there is little or no HAZ around the exposed site, resulting in less damage to the substrate material than conventional CO2, nanosecond, and long pulse lasers This allows for fine control of feature sizes not possible with CO2 and long pulse lasers, enabling the fabrication of high-precision and high-quality MNT devices [28,39,44,50,51]. Recent investigations in FLMP have included efforts on how to effectively control the processing parameters, such as CNC speed, fluence (energy density), focused laser beam size, wavelength, and repetition rate [47,52,53,54,55,56,57] These processing parameters have a significant effect on the properties of the resultant material etch parameters, such as etch profile (including cleanliness of the cut-edge), depth, feature size resolution, and surface roughness. The obtained relations were used as models to guide the fabrication of 3D multi-depth features into a borosilicate glass substrate with 4 different depths for use as a reservoir micromodel
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