Cost-Effective Three-Dimensional Printing of Visibly Transparent Microchips within Minutes

TLDR

The authors used the printer to fabricate a micromixer, gradient generator, droplet extractor, and isotachophoresis device, demonstrating its applicability in microfluidics. The system employs dynamic mask projection stereolithography with a fully automated setup that prints up to 43 mm × 27 mm × 180 mm at 20 mm/h in height, uses a colorless resin with >60 % light transmittance for optical detection, and an electrically insulating material for electrophoretic separations, enabling rapid concept‑to‑chip fabrication. The printer achieved one‑step fabrication of transparent 3D microfluidic devices at a cost of $138 for 500 mL resin, produced monolithic microchannels with a minimal cross‑sectional area of 250 µm (200 µm for positive templates), and enabled a nitrate analysis device with extended linear range through integrated mixing and gradient units.

Abstract

One-step fabrication of transparent three-dimensional (3D) microfluidic to millifluidic devices was demonstrated using a commercial 3D printer costing $2300 with 500 mL of clear resin for $138. It employs dynamic mask projection stereolithography, allowing fast concept-to-chip time. The fully automated system allows fabrication of models of up to 43 mm × 27 mm × 180 mm (x × y × z) at printing speeds of 20 mm/h in height regardless of the design complexity. The minimal cross sectional area of 250 μm was achieved for monolithic microchannels and 200 μm for positive structures (templates for soft lithography). The colorless resin's good light transmittance (>60% transmission at wavelengths of >430 nm) allows for on-chip optical detection, while the electrically insulating material allows electrophoretic separations. To demonstrate its applicability in microfluidics, the printer was used for the fabrication of a micromixer, a gradient generator, a droplet extractor, and a device for isotachophoresis. The mixing and gradient formation units were incorporated into a device for analysis of nitrate in tap water with standard addition as a single run and multiple depth detection cells to provide an extended linear range.