| Summary: | 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 (<inline-formula><math display="inline"><semantics><mrow><msub><mrow><mi>LF</mi></mrow><mrow><mi>av</mi></mrow></msub></mrow></semantics></math></inline-formula>), and computer numerically controlled (CNC) processing speed (<inline-formula><math display="inline"><semantics><mrow><msub><mrow><mi>PS</mi></mrow><mrow><mi>CNC</mi></mrow></msub></mrow></semantics></math></inline-formula>), was studied. A linear etch depth dependence on <inline-formula><math display="inline"><semantics><mrow><msub><mrow><mi>LF</mi></mrow><mrow><mi>av</mi></mrow></msub></mrow></semantics></math></inline-formula> was determined while a three-phase exponential decay dependence was obtained for <inline-formula><math display="inline"><semantics><mrow><msub><mrow><mi>PS</mi></mrow><mrow><mi>CNC</mi></mrow></msub></mrow></semantics></math></inline-formula>. The accuracy of the method was investigated by using the etch depth dependence on <inline-formula><math display="inline"><semantics><mrow><msub><mrow><mi>PS</mi></mrow><mrow><mi>CNC</mi></mrow></msub></mrow></semantics></math></inline-formula> 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.
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