A team of researchers from the University of Bristol has developed a novel low-cost and open-source 3D printing process for producing microfluidic devices.
A microfluidic chip is a set of micro-channels etched or molded into a material, such as glass, silicon, or in this case, PolyDimethylSiloxane (PDMS), which are connected to the outside world by inputs and outputs pierced through the chip. Through these holes, liquids or gases can be injected and removed by external active or passive systems for biomedical field applications such as laboratories-on-a-chip (LOC), cell biology research, and protein crystallization.
Requiring only simple domestic equipment and a standard desktop 3D printer, and having been developed in free-to-use software, the researchers’ process reduces the cost and complexity of fabricating microfluidics to make the field more accessible.
The team believes their approach could drastically lower the threshold for research and education into microfluidics while making the rapid prototyping of affordable LOC diagnostic technology possible at the point-of-care (POC).
3D printing and microfluidics
For decades, LOC technology has been heralded to answer a range of biological, chemical, and healthcare challenges. However, it is yet to see meaningful adoption and deployment due to the cost both at the research level and the mass-manufacturing stage.
LOC technologies are supported by the field of microfluidics, which is seeing an increasing exploration of 3D printing techniques to advance the technology and increase its accessibility.
In 2018, researchers from New York Genome Center and New York University developed an open-source 3D printed droplet microfluidic control instrument which was reportedly up to 200 times cheaper than other comparable instruments. Designed to identify and target the correct cells to treat diseases such as Rheumatoid Arthritis, the instrument could be obtained and assembled for around $600.
Elsewhere, a process has been developed to 3D print microfluidic devices integrated with fluid handling and functional components. Developed by the Singapore University of Technology and Design, the technique aimed to enable the rapid prototyping of microfluidics for LOC applications in chemical testing and cell analysis.
Most recently, researchers from UC Davis unveiled a new approach to 3D printing using microfluidics, which involved deploying a droplet-based microfluidic system to efficiently 3D print finely-tuned flexible materials. Possible applications for the technology include soft robotics, tissue engineering, and wearable technology.
Fabricating the microfluidic devices
The researchers began by 3D printing interconnecting microchannel scaffolds with an Ultimaker 3 Extended 3D printer using PLA, which were then thermally bonded to a glass substrate in the desired configuration to create a microfluidic device master mold.
The microchannels were designed in a range of modular patterns, with each featuring interlocking ball-socket connector ends, using Ultimaker’s Cura open-source slicing software. These ends were developed to mimic puzzle pieces. Successive modules could be arranged in any desired configuration, enabling creating more sophisticated microfluidic systems using a small number of simple modules. A key aspect of this part of the researchers’ process is that it is easy and clear to replicate for non-expert users.
The 3D printed microchannel modules were then mounted onto standard 1mm-thick glass microscope slides into the desired configuration, using the ball-and-socket connectors. The channels were then heated for around a minute to bind them to the glass with a weighted slide placed on top to prevent deforming and shrinking. After heating, the slides were partially fused and placed weighted-side down onto a metal plate to rapidly cool the weighted slide and remove it from the mold.
The master mold can be used again and again to produce microfluidic devices in PDMS. Post-printing, the master mold fabrication process can be completed in less than five minutes, allowing the method to be used for both formal and informal learning environments.
To ensure the proposed technique is fully democratized, the researchers developed an open-source Autodesk Fusion add-in which allows any user to design and export interconnecting microfluidic channel scaffolds for 3D printing. Using this plugin, a user can go from a microfluidic channel design to a completed microfluidic channel without requiring CAD software expertise or time and resource-intensive techniques or equipment.
Users can prototype interconnecting microfluidic channels down to 100 μm resolution in width, either through printing their own designs or choosing from a vast library of microchannel scaffolds listed in the add-in. A protocols.io instruction set has also been made available detailing the researchers’ full process, with links to the up-to-date add-in and profiles.
Using this technique, users can fabricate microfluidic devices from PDMS with only household equipment and no hazardous chemicals, thereby making microfluidic experimentation accessible to schools, hobbyists, and researchers no matter their resources. The team hopes that this approach will be adopted by researchers and educators worldwide to “help to inspire the next generation of lab-on-a-chip developers.”
Furthermore, the researchers believe their technique could pave the way for “truly affordable” LOC healthcare diagnostic testing, which can be performed at the point-of-care, through applying the microfluidic PDMS channels directly to any cleaned glass surface, such as a mobile phone screen or a car windshield.
Further details on the study can be found in the paper titled “Negligible-cost microfluidic device fabrication using 3D printed interconnecting channel scaffolds” published in the Plos One journal. The study is co-authored by H. Felton, R. Hughes, and A. Diaz-Gaxiola.
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Featured image shows proposed microfluidic master mould fabrication process. Image via University of Bristol.