How 3D-printing technology be used to fabricate low-cost microfluids on mm-scale?

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The integration of microfluids and nanotechnology for developing miniaturized devices called Lab-on-a-chip (LOC) has been widely adopted into several applications such as PCR on a chip to accelerate DNA amplification by more than ten times. The field of microfluids has laid a solid foundation for lab-on-a-chip devices that enable the manufacturing of millions of microchannels measuring micrometers. One of the most common methodologies for microfluid channel design and fabrication is the photolithography masking of a channel negative on a crystalline silicon wafer. This is then used as a mould for the biocompatible polymer such as polydimethylsiloxane (PDMS). However, these advanced fabrication methods are expensive and time-consuming for which the research for low-cost microfluidic and LOC technology has attracted attention in recent times. Some of these solutions include the use of 3D-printed structures, milled glass and acrylic, and xurography. 

The study carried out by N. Bhattacharjee et al. [1] discussed the limitations of 3D printing for microfluid channels, and these challenges for Material Extrusion (MEX) (commonly referred to as Fused Deposition Modelling and Fused Filament Fabrication) printed microfluid channels were– the printed parts could not be joined at channel intersections, weak seals occur between layers, and size of the extruded material is larger than channel sizes used in microfluids. Several research works focused on mitigating these issues and improving the technology to bring in accuracy and affordability. In the paper presented. we developed a low-cost, highly accessible fabrication technique for manufacturing cheap microfluidic channel moulds using MEX 3D printing and interconnecting module design [2]. With the development of the new methodology, the team believes to have made progress toward overcoming the challenges mentioned by N. Bhattacharjee et al.

Using open-source tools for microfluidic channel design

In the research paper titled, “Negligible-cost microfluidic device fabrication using 3D-printed interconnecting channel scaffolds,” the work carried out demonstrates how 3D printing can be used to fabricate microfluidic devices on a micrometer scale down to approximately 100µm. The following image describes the whole process of leveraging the technology through open-source materials while reducing the cost associated with the designing methodology. The technique also aims to reduce entry barriers for microfluidic device design, enabling faster prototyping for a wide range of applications. 

Process of using 3D-printing technology to fabricate low-cost microfluidic channel design [Image Credit: Research Paper]

The fabrication process is divided into two stages– the first involves 3D printing and interconnecting microchannel scaffolds onto a build place, and after the removal from the printer, the second stage involves thermal bonding of these microchannel modules to a glass substrate in the desired configuration. This master mould can then be used and reused to produce microfluidic devices in PDMS. The technique uses an open-source tool, Autodesk Fusion, to allow users to generate microfluidic channel designs using simple dropdown boxes and numerical inputs for a range of designs. The click-and-connect ball-and-socket joints are integrated to allow the combination of simple devices into existing complex assemblies. The ready .stl file can be used for fabrication. 

“Direct applications of the developed technology have thus far been limited to proof-of-concept examples, such as mixers (above) and droplet generators (below),” the team notes. “Initial results have, however, been very promising and the aim is to use the devices in real-world applications soon. Work is currently being completed hoping to apply the technology to clinical testing and research.”

Practical use of the fabrication technique in PDMS

For practical use, the team manufactured two microfluidic devices and tested them on PDMS. A fluid mixing device (dye-mixing) was manufactured using the interconnecting module design. The channels were manufactured from scaffold modules with a CAD-designed geometry of 350x350μm and thermally bonded to produce microfluidic channels. “Droplet generator scaffolds were printed at 350μm and 100μm widths using the open-source Autodesk Inventor add-in and used to fabricate devices in PDMS.”

With the proposed method for rapid prototyping of low-cost soft-lithographic channel moulds for fabrication of microfluidic channels in PDMS, the users will be able to print their own designs using the open-source CAD tool add-in. The methodology also allows users to fabricate microfluidic devices from PDMS with household equipment and no hazardous chemicals.  “This simple yet innovative approach dramatically lowers the threshold for research and education into microfluidics and will make possible the rapid prototyping of point-of-care lab-on-a-chip diagnostic technology that is truly affordable the world over,” the research concludes.

The research was published in PLOS ONE under open-access terms for public viewing.

References

[1] Bhattacharjee N., Urrios A., King S., and Folch A., “The upcoming 3D-printing revolution in microfluidics,” Lab Chip, vol. 16, no. 10, pp. 1720–1742, 2016, https://doi.org/10.1039/c6lc00163g PMID: 27101171

[2] Felton H, Hughes R, Diaz-Gaxiola A (2021) Negligible-cost microfluidic device fabrication using 3D-printed interconnecting channel scaffolds. PLOS ONE 16(2): e0245206. https://doi.org/10.1371/journal.phone.0245206  

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