Introduction: This research presents an advanced method for fabricating microfluidic nanochips using high-precision CNC machining, specifically for Pulmonary Arterial Hypertension (PAH) research. By utilizing PMMA and integrating CAD, CAM, and HSM processes, we achieved intricate designs and tight tolerances essential for PAH studies. Our method enhances production efficiency and scalability, marking a significant advancement in microfluidic technology.
Materials and
Methods: We used black cast acrylic sheets (24" x 36" x 3/16") and clear scratch- and UV-resistant acrylic bars. End mills (0.0040", 0.0390", and 1/4"), double-sided adhesive tape, and a jigsaw were employed, along with a CNC Mini-Mill/3, cordless jig saw, and LEICA DMi8 microscope. The setup involved cutting the acrylic sheet to size, securing it to the CNC bed with double-sided tape, and ensuring flatness with a 1/4" endmill. The microfluidic chip, designed with SolidWorks 2023, measured 24mm x 21.6mm x 3.175mm, with inlet and outlet holes for fluid flow. Channels and hexagonal pillars were designed with radii and distances to match machining tolerances. CAM processes determined tools and cutting parameters, optimizing spindle speed (10,800 rpm) and feed rates for PMMA. We calculated key parameters such as feed per tooth, cutting feed, and cutting speed to maximize efficiency and minimize tool breakage. The cover slide, designed to enclose the chip's channels and pillars, was treated with 0.5mL ethanol per 323 mm² bonding area and UV light for 10 minutes to promote bonding. After UV treatment, the cover slide was aligned and pressed onto the chip for two minutes, forming a secure bond. The chip featured five microchannels, each 100μm wide, separated by hexagonal pillars 200μm apart and 150μm high. This method integrated CAD, CAM, and HSM processes, enhancing the precision and scalability of microfluidic chip production for PAH research. The detailed design ensured accurate replication of complex structures necessary for PAH studies.
Results, Conclusions, and Discussions: Initially, a 0.1016mm square endmill operating at 10,800 rpm with a cutting feed rate of 60.3504mm/min created channels on the stock using the 2D pocket function, taking 50 minutes per chip. The same endmill then cut the 200μm inter-pillar regions in 4 minutes per chip, while removing burrs around the inlet and outlet bridges took 3 minutes per chip. Refining the channel perimeter with a 2D contour function took 2.5 minutes per chip. Clearing inlet and outlet holes with a 0.9906mm endmill at 9011rpm took 3.5 minutes per chip, and detaching the chip from the stock took 6 minutes per chip, totaling 1 hour and 9 minutes per chip. Microscopic analysis revealed material residue and burrs affecting hexagonal pillars' quality. The refined CAM process used two flat endmills, with the larger 0.9906mm tool clearing inlets and outlets in 1 minute per chip, followed by a 0.1778mm tool for channels and pillars, improving machining time by 90%. Consistent spindle speed (10,800rpm) and optimized feed rates enhanced precision, resulting in well-defined hexagonal pillars and clear channels. Functional tests with Trypan blue solution confirmed a 95% success rate in leak prevention. This approach increased production efficiency and improved chip quality. The study optimized CAD, CAM, and CNC processes for microfluidic chip fabrication, reducing machining time from 1 hour and 9 minutes to 12 minutes per chip and enhancing structural precision. Future research could explore surface smoothing with ball endmills and varying tool diameters to further enhance chip performance.
