Three-dimensional-printing for microfluidics or the other way around?

Abstract

As microfluidic devices are designed to tackle more intricate tasks, the architecture of microfluidic devices becomes more complex, and more sophisticated fabrication techniques are in demand. Therefore, it is sensible to fabricate microfluidic devices by three-dimensional (3D)-printing, which is well-recognized for its unique ability to monolithically fabricate complex structures using a near-net-shape additive manufacturing process. Many 3D-printed microfluidic platforms have been demonstrated but can 3D-printed microfluidics meet the demanding requirements in today's context, and has microfluidics truly benefited from 3D-printing? In contrast to 3D-printed microfluidics, some go the other way around and exploit microfluidics for 3D-printing. Many innovative printing strategies have been made possible with microfluidics-enabled 3D-printing, although the limitations are also largely evident. In this perspective article, we take a look at the current development in 3D-printed microfluidics and microfluidics-enabled 3D printing with a strong focus on the limitations of the two technologies. More importantly, we attempt to identify the innovations required to overcome these limitations and to develop new high-value applications that would make a scientific and social impact in the future.

Keywords: 3D-printing; Bioprinting; Microfluidics.

Figure 1

A three-dimensional (3D)-printed true 3D microfluidic device with standard fluidic coupling. (A) The schematic illustration of the 3D-printed device showing the cross-section of the 3D helical channel. (B) The cross-section of the channel is trapezoid in shape. (C) The actual 3D helical microfluidic device. Reproduced from Ref. Lee et al.[27] with the permission granted under the creative common license.

Figure 2

Three-dimensional (3D)-printed active microfluidic membrane valve. (A) The valve is open and closed configuration. (B) Fluidic control with the valve. (i) Valve 1 (V₁, left) is open and valve 2 (V₂, right) is closed. Only blue liquid flows in the central channel. (ii) V1 is closed and V2 is open. Only red liquid flows in the central channel. (iii) Both valves are open. A mixture of blue and red liquids flow in the central channel. Reproduced from Ref. Au et al.[20] with permission from Royal Chemical Society.

Figure 3

Three-dimensional (3D)-printed modular microfluidics. (A) Individual microfluidic module. (B) A microfluidic droplet generator is constructed by cascading three 3D-printed modules. (C) Several complex 3D microfluidic configurations constructed from 3D-printed microfluidic modules. Reproduced from Ref. Bhargava et al.[39] with permission from the National Academy of Science (US). Copyright (2015) National Academy of Sciences.

Figure 4

Microfluidics-enabled three-dimensional-printing. (A) Two-inlet microfluidic devices used as the printhead. Two bioinks are combined into a single micro hydrogel filament for extrusion. (B) Hydrogels printed using the microfluidic printhead shown in A. Each filament consists of two bioinks combined by the microfluidic printhead. (C) A three-inlet microfluidic printhead with passive mixer. (i) Schematic illustration of bioprinting with the microfluidic printhead. (ii) Herringbone passive mixer in the microfluidic printhead. (D) High-throughput parallel microfluidic printhead. (i) A high-degree of parallel printing with a bifurcating microfluidic network. (ii) and (iii) Microfilament arrays printed with the microfluidic printhead. A and B are reproduced from Ref. Colosi et al.[50] with permission from Wiley. C is reproduced from Ref. Serex et al.[51] with the permission granted under the creative common license. D is reproduced from Ref. Hansen et al.[52] with permission from Wiley.