Precision hot-melt freeform 3D printing for monolithic multilayer microfluidics

Miniaturization and integration of assays, chemical synthesis, and cell culture models onto microfluidic chips is an intensive area of research. Despite the diversity of these applications, the vast majority of microfluidic devices are fabricated from polydimethylsiloxane (PDMS) using the same lithography methods described in 1998. Limitations of the lithography/PDMS architecture include the requirement for rectangular channels of fixed height and the necessity of bonding multiple layers to make 3D constructs. The problem of fabricating networks of small tubes in diverse media is ubiquitous, yet there is still no “black box” that laboratories can buy to turn microfluidic designs into microfluidic chips. 3D printing predates soft lithography, yet only recently have 3D printing methods been applied to the fabrication of microfluidic devices. I will present a custom printer, which extrudes filaments of water-soluble, self-supporting material along 3D toolpaths. By printing the desired channel geometry, casting a curable material around it, then dissolving away the soluble printed material, it is possible to make complex, 3D networks of cylindrical channels. I develop design rules for constructing these sacrificial molds using a 3-axis stage, algorithms for processing designs into toolpaths, and a novel method for precision extrusion. To prove that channels can be fabricated with good fidelity, I produce a monolithic, multilayer microfluidic device that mixes two components in ratios ranging from 1:100 to 100:1. Due to its compatibility with a broad range of materials, freeform 3D printing may enable the construction of many different organ-on-chip models as well as micro-electromechanical systems, electrically small antennas, and polymer stents