A Systematic Approach for Developing 3D High-Quality PDMS Microfluidic Chips Based on Micromilling Technology

Abstract

In recent years, there has been an increased interest in exploring the potential of micro-and mesoscale milling technologies for developing cost-effective microfluidic systems with high design flexibility and a rapid microfabrication process that does not require a cleanroom. Nevertheless, the number of current studies aiming to fully understand and establish the benefits of this technique in developing high-quality microsystems with simple integrability is still limited. In the first part of this study, we define a systematic and adaptable strategy for developing high-quality poly(methyl methacrylate) (PMMA)-based micromilled structures. A case study of the average surface roughness (Ra) minimization of a cuboid column is presented to better illustrate some of the developed strategies. In this example, the Ra of a cuboid column was reduced from 1.68 μm to 0.223 μm by implementing milling optimization and postprocessing steps. In the second part of this paper, new strategies for developing a 3D microsystem were introduced by using a specifically designed negative PMMA master mold for polydimethylsiloxane (PDMS) double-casting prototyping. The reported results in this study demonstrate the robustness of the proposed approach for developing microfluidic structures with high surface quality and structural integrability in a reasonable amount of time.

Low-cost microfluidics: Towards affordable environmental monitoring and assessment

“…Unlike 3D printing, micromilling is a subtractive manufacturing technique that removes the materials from the bulk to create the desired structures. The prepared parts can be bonded to a substrate to create the final enclosed microfluidic device (Hossain and Rahman, 2018;Rahim and Ehsan, 2021), or it can be used as a mold for PDMS (Jiménez-Díaz et al, 2019;Javidanbardan et al, 2021). Similar to many other low-cost fabrication methods, micromilling does not require a cleanroom and is relatively fast, greatly expediting the manufacturing processes especially for prototyping tests (Faustino et al, 2016;Nguyen et al, 2019).…”

“…Similar to many other low-cost fabrication methods, micromilling does not require a cleanroom and is relatively fast, greatly expediting the manufacturing processes especially for prototyping tests (Faustino et al, 2016;Nguyen et al, 2019). Currently, many materials have been explored to create microfluidic devices using micromilling, among which PMMA and aluminum are two most popular materials (Jiménez-Díaz et al, 2019;Nguyen et al, 2019;Behroodi et al, 2020;Javidanbardan et al, 2021;Saptaji et al, 2021). The micromilled molds made of aluminum can be used for casting multiple times, which could further reduce the cost of the final device (Guckenberger et al, 2015;Nguyen et al, 2019).…”

“…For example, the milling bits used in micromilling are prone to breaking especially when high resolution (e.g., 25 µm) is required (Charles et al, 2018;Leclerc, 2021). In addition, complex 3D features and designs may not be suitable for micromilling, even though customized milling bits may be able to create structures with preset shapes (Ku et al, 2018;Javidanbardan et al, 2021). Micromilling only removes the materials from external surfaces, therefore bonding with other substrates is inevitable to create enclosed microchannels.…”

5-axis CNC micro-milling machine for three-dimensional microfluidics

“…Currently, 3-axis milling has been reported for prototyping and fabricating microfluidics, but this technique is limited in geometric complexity. [14][15][16][17][18] 5-axis systems expand the capabilities of traditional 3-axis systems by including two rotational axes, allowing the workpiece to be milled from virtually any position. 5-axis systems can mill overhanging geometries, curved surfaces, and inclined features.…”

Study of PDMS Microchannels for Liquid Crystalline Optofluidic Devices in Waveguiding Photonic Systems

“…Importantly, a mold with sufficient quality and specific geometry is needed to fabricate optofluidic structures in PDMS using a casting technique. There are many methodologies to manufacture molds [11], including 3D printing [12][13][14], micromilling [11,12,15,16], and capillary film processing [17]. In the same context, photolithography is the most widely used for complex and precise structures [18,19].…”