Controlled Depth Micro-Milling of 304 Stainless Steel Rods Using Abrasive Slurry Jet Machining to Create Curvilinear Micro Channels

Using a microfluidic device called Lab-on-a-Chip (LOC) to sort particles based on size and density forms the basis for a filterless filter. However, fabricating these micro-sized curved channels is challenging because stereolithographic processes and PDMS molding techniques limit the creation of curvilinear channels in a two-dimensional plane that must either converge or diverge. This limits the length of the channel for a given range of radius of curvature. This research uses a novel method to machine curvilinear channels directly onto a 5 mm 304SS rod, establishing a foundation to produce a Lab-on-a-Rod (LOR) and eliminating the need for contact masks. It maintains a constant radius of curvature and allows for a channel length limited only by the 250 mm length of the rod. An apparatus was designed to machine curvilinear channels using Abrasive Slurry Jet Machining (ASJM) and a modified lathe mechanism capable of withstanding the rigors of the harsh ASJM environment and ensuring repeatability from experiment to experiment. The resulting design, named the Abrasive Slurry Jet Machining Lathe Apparatus (ASJMLA), was used in three experiments: repeated machining passes with no angle of attack (α = 90°), repeated passes using α = 60° and α = 75°, and varying the number of machining passes along a continuous channel to create discrete depths using α = 90°. The research demonstrated that machining microchannels onto a rod is feasible. It showed that the depth of the channel correlates directly with the number of repeated passes, an increase in the angle of attack produces deeper channels on average, and it is possible to produce channels with six discrete depths within a continuous length of channel. This forms the basis for fractionating microfluidic flows to collect discrete samples.