It’s possible to use 3D printing to create microfluidic devices, which are tiny ‘lab on a chip’ tools that use microscopic channels to work out small structures like cells and disease biomarkers in liquid samples such as blood; they can also quickly and precisely analyze chemicals with small volumes. But the devices are expensive and difficult to make, due to their complex geometry, and while 3D printed molds have been used to construct microfluidics platforms, 3D printing itself does present some limitations with overall size and materials. But researchers at Brigham Young University (BYU) in Utah are now the first to use 3D printing to fabricate a working microfluidic device that’s small enough to be effective at a scale less than 100 micrometers.
“Others have 3D-printed fluidic channels, but they haven’t been able to make them small enough for microfluidics. So we decided to make our own 3D printer and research a resin that could do it,” said BYU electrical engineering professor Greg Nordin.
Other researchers working on 3D printed microfluidics have been unable to create labs on a chip with flow channel cross sections smaller than 100 micrometers. But professors at BYU have some prior experience with 3D printing tiny tools, and this research team has already produced labs on a chip with sections as small as 18 by 20 micrometers. In addition to designing a low-cost, custom resin, the 3D printer that the team built is able to print at a much higher resolution: it uses a 385 nm LED, which “dramatically increases the available selection of UV absorbers for resin formulation compared to 3D printers with 405 nm LEDs,” as BYU reports.
The team published a paper on their accomplishment, titled “Custom 3D printer and resin for 18 μm x 20 μm microfluidic flow channels,” in the Lab on a Chip academic journal; co-authors include Nordin; BYU chemistry professor Adam Woolley; Hua Gong, a BYU PhD student who was in charge of the experimental work that made the 3D printing advancement possible; and BYU undergraduate student Bryce Bickham, who spent weeks in the university library to find the perfect material for the team’s custom 3D printing resin.
The abstract reads, “In this paper we demonstrate that a custom digital light processor stereolithographic (DLP-SLA) 3D printer and a specifically-designed, low cost, custom resin can readily achieve flow channel cross sections as small as 18 μm × 20 μm. Our 3D printer has a projected image plane resolution of 7.6 μm and uses a 385 nm LED, which dramatically increases the available selection of UV absorbers for resin formulation compared to 3D printers with 405 nm LEDs. Beginning with 20 candidate absorbers, we demonstrate the evaluation criteria and process flow required to develop a high-resolution resin. In doing so, we introduce a new mathematical model for characterizing the resin optical penetration depth based only on measurement of the absorber’s molar absorptivity. Our final resin formulation uses 2-nitrophenyl phenyl sulfide (NPS) as the UV absorber. We also develop a novel channel narrowing technique that, together with the new resin and 3D printer resolution, enables small flow channel fabrication. We demonstrate the efficacy of our approach by fabricating 3D serpentine flow channels 41 mm long in a volume of only 0.12 mm3, and by printing high aspect ratio flow channels <25 μm wide and 3 mm tall. These results indicate that 3D printing is finally positioned to challenge the pre-eminence of methods such as soft lithography for microfluidic device prototyping and fabrication.”
The team’s work is a big breakthrough in terms of inexpensively mass-producing the tiny 3D printed medical diagnostic devices, and the researchers explained that they are “laying the foundation” so that 3D printing technology is able to take on conventional methods used in microfluidic development and prototyping, like hot embossing and soft lithography. According to Nordin, digital light processing stereolithography (DLP-SLA) is a good low-cost approach to 3D printing microfluidic devices; this method utilizes a micromirror array chip, which can often be found in consumer projectors, to create the optical pattern for each layer of printing.
Woolley says that the team’s work is representative of a major improvement – by a factor of 100 – on the size of the features that 3D printed microfluidics makes possible. In addition, the BYU team’s approach is able to cut down the usual time and work of creating microfluidic devices – they can print a device in half an hour, without needing to use a special clean room environment.
“It’s not just a little step; it’s a huge leap from one size regime to a previously inaccessible size regime for 3D printing. It opens up a lot of doors for making microfluidics more easily and inexpensively,” Woolley said.
Woolley is working on using lab-on-a-chip devices to detect biomarkers that are related to preterm birth, and recently submitted a proposal with Nordin to the National Institutes of Health to work on developing the BYU team’s 3D printed microfluidics approach for preterm birth prediction. Discuss in the 3D Printed Microfluidics forum at 3DPB.com.[Source/Images: Brigham Young University]
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