Oct 30, 2017 | By Benedict

Researchers at MIT have developed a 3D printed nozzle device for producing nanofiber meshes. The device, made with a DLP 3D printer, matches the speed and power of its MIT-made predecessor, but produces more uniform fiber diameters at a much lower cost.

The creation of nanofiber meshes is useful in a wide range of applications, from water filtration to tissue engineering to solar energy. But the conditions needed to make the meshes can often be hard to obtain: an airlocked clean room has traditionally been required for accurate mesh fabrication, making the process impractical and even impossible for many research purposes.

A new 3D printed device, developed by researchers at MIT, could be about to make nanofiber mesh creation simpler, cheaper, and more accurate.

The tiny microfluidic device consists of an array of small nozzles through which a fluid mixture containing polymer particles can pass. The nozzles are arranged into two rows, slightly offset from one another, which enables the fabrication of aligned nanofibers.

Such aligned nanofibers are particularly useful for tissue scaffolding, but the device can also be adjusted to accommodate unaligned nanofibers, which actually speeds up the process considerably.

The MIT researchers involved in the research strongly believe that simple 3D printed devices like this nozzle system can radically shake up the practice of nanofiber creation, or “electrospinning.”

“My personal opinion is that in the next few years, nobody is going to be doing microfluidics in the clean room,” said Luis Fernando Velásquez-García, a principal research scientist in MIT’s Microsystems Technology Laboratories and senior author on the group’s new research paper. “There’s no reason to do so: 3D printing is a technology that can do it so much better.”

One big advantage of additive manufacturing is that, by 3D printing the new microfluidic device, the MIT researchers were able to quickly test and revise new designs.

The development process for the 3D printed nozzle device took around a year, during which the team 3D printed around 70 iterations. For non-printed microfabricated devices, it can take around two years, during which only two or three designs can be fully tested.

Velásquez-García added that 3D printing offers a “better choice of materials, with the possibility to really make the structure that you would like to make,” while also being much more cost-effective than the “incredibly expensive” process of using a clean room.

The MIT researchers used a $3,500 (presumably including projector costs) Solus DLP 3D printer, made by Reify 3D, to fabricate their device.

Devices like solar cells can benefit from nanofibers because of their high ratio of surface area to volume. So can materials that need to be permeable only at very small scales, like water filters, and so can lightweight and strong materials like body armor.

To get the most out of any of these applications, however, the fabricated nanofibers need to be of consistent diameter—something the new 3D printed device is excellent at ensuring.

“If you have a significant spread [of diameters], what that really means is that only a few percent are really working,” Velásquez-García explained. “Example: You have a filter, and the filter has pores between 50 nanometers and 1 micron. That’s really a 1-micron filter.”

The 3D printed device is so good at regulating diameters of the nanofibers because its emitters—the tubular sections through which the polymer mix is feed to become a nanofiber—are “internally fed.” The emitters have holes bored through them, and are filled with the fluid by hydraulic pressure. Once fully filled, an electric field pulls out the fluid mix as tiny fibers.

With previous designs, the fibers were sometimes pulled out before the emitters were fully filled, because the “externally fed” system was not as effective.

The new design also uses coiled, tapered channels, which are key to keeping diameters consistent.

Excitingly, the researchers plan to continue their studies, suggesting that 3D printing could be used to fabricate electrospinning sources made of more resilient 3D printed materials, such as ceramics. They add that the emitters could include more complex geometries, and even suggest that multi-material spinning could be achieved to create smart materials with several desirable properties.

The research paper, “3D printed multiplexed electrospinning sources for large-scale production of aligned nanofiber mats with small diameter spread,” was written by Velásquez-García and postdocs Erika García-López and Daniel Olvera-Trejo. It has been published in Nanotechnology.



Posted in 3D Printing Application



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