Wall Deformation and Minimum Thickness Analysis in Micro-Milled PMMA Microfluidic Devices: A Comparative Study of Milling Strategies

Polymethyl methacrylate (PMMA) is widely used in microfluidic device fabrication due to its chemical resistance, low cost, optical transparency, and manufacturing compatibility. However, limited research exists on wall deformations and the minimum achievable wall thickness between machined channels in PMMA via micro-milling. As microfluidic devices require tightly spaced features, identifying the minimum machinable wall thickness is essential for miniaturization and multifunctional integration, enabling rapid and reproducible biomedical testing. This study presents experimental data and finite element modeling on wall deformation characteristics—wall deviation angle, average wall thickness, and minimum machinable wall thickness—between micro-milled PMMA channels. Micro end-milling was performed with varying feed rates, wall thicknesses (50 $\mathsf{\mu }$m, 100 $\mathsf{\mu }$m, 150 $\mathsf{\mu }$m), and milling strategies (direct, radial, axial depth). ANOVA was used to assess parameter influence, and finite element modeling simulated wall bending under the radial depth strategy. Results show that wall thickness, feed rate, and milling strategy significantly affect wall deviation and thickness. Experimental and simulation data revealed consistent trends: 50 $\mathsf{\mu }$m walls showed cracking, base fractures, and geometric deviations, while 100 $\mathsf{\mu }$m and 150 $\mathsf{\mu }$m walls retained structural integrity. A minimum wall thickness of 150 $\mathsf{\mu }$m is necessary to ensure reliable sealing in microfluidic devices.