MIT researchers develop low-cost ‘DefeXtiles’ under-extrusion 3D printing method 

Researchers from the Massachusetts Institute of Technology have demonstrated a novel ‘under-extrusion’ method of 3D printing textile products. 

The MIT team’s process essentially uses the stringing behavior that occurs in extruded polymers, to fabricate clothing items featuring small gaps, providing them with enhanced flexibility. Utilizing their simple technique, which doesn’t require any software or hardware upgrades, the scientists believe that it could be possible to 3D print garments as a means of reducing waste in the fashion industry. 

“The simplicity of this approach is what makes it so powerful,” explained the team on their website. “We have been able to 3D print dresses for clothing design prototyping, tough badminton shuttlecocks and full-sized garments—such as a skirt—to help users “try on” clothes before ordering online.”

The growing role of additive within the textile industry 

As the world moves towards a more sustainable future, people are starting to pay greater attention to the clothes they wear, and how they’re manufactured. Most garments are currently produced through a machine-knitting process, which allows the fabric to be formed and shaped at the same time, but this approach has many limitations. 

Not only is the necessary machinery expensive, but outside of industrial factories, it can be very difficult to produce clothing with complex forms. 3D printing on the other hand, is increasingly being adopted within the fashion industry, as a more material-efficient alternative to conventional sewing and knitting techniques. 

Stratasys for instance, has developed its direct-to-textile PolyJet Technology, and deployed it alongside designers Ganit Goldstein and Julia Koerner to 3D print a specialist fashion line. Elsewhere, Mingjing Lin, a designer from the Royal College of Art (RCA), has fabricated various drapeable designs, while the Milan-based Chiara Giusti has worked with Superforma Fablab to 3D print her TECHNĒ range. 

According to the MIT team, while these approaches are continuing to gain traction, some of the resulting garments aren’t as thin, flexible or breathable as off-the-peg clothing. What’s more, given that many prototype processes are based on new materials or custom hardware, they aren’t accessible to those with an everyday Fused Deposition Modelling (FDM) setup. 

The MIT team found that changing the nozzle's print direction meant they could adjust the placement of filament 'blobs.' Image via MIT.
The MIT team found that by changing the nozzle’s print direction, they could adjust the placement of a filament’s ‘globs.’ Image via MIT.

The MIT ‘DefeXtiles’ 3D printing technique

The researchers’ alternative DefeXtiles strategy seeks to utilize under-extrusion, which is usually seen as a defect within FDM 3D printing, as a means of creating thinner and more flexible textiles. These defects (also known as stringing) are caused when too little material is extruded to form a solid layer, but there’s enough left to allow periodic interlayer adhesion.

When this happens, the polymer begins to form small ‘globs’ of material that remain connected via tiny strands, and as printing continues, these stack on top of each other, causing stringing to occur. By alternating the print direction, the MIT team found that they could change the shape of these connecting strands, causing gaps to appear, and yielding textiles with greater breathability. 

Given that the team’s novel process doesn’t require any specialized hardware or post-processing steps, they theorized that it could be compatible with a range of systems and polymers. In order to ascertain just how effective their technique could be, the researchers carried out test prints, to optimize their system’s parameters and characterize the resulting fabrics. 

Several 5cm x 5cm polymeric square swatches were used to find the optimal print settings, and tests showed that as the print speed was increased, the density of the fabric became less and less predictable. Effectively, the MIT team’s technique was found to behave like many 3D printing methods, in that there was a clear trade-off between speed and quality.

As a result, the researchers recommended that adopters use a higher extrusion multiplier or slower print speed along with a TPU material, to create textiles with the optimal level of flexibility. 

The researchers successfully 3D printed a variety of objects, including a white skirt (pictured). Photo via MIT.
The researchers successfully 3D printed a variety of objects, including a white skirt (pictured). Photo via MIT.

Finding new applications for under-extrusion

Having optimized their 3D printing setup, the MIT team began to experiment with fabricating larger and more complex textile designs. Initially, the researchers printed flat sheets of PLA and discovered that they needed support structures, but curved sheets could be created in rolls, which made them self-supporting. 

Building on this approach, the team found they were able to fabricate more complex 3D shapes, featuring gaps or overhangs without needing to include support structures. What’s more, using CAD software, the scientists discovered they could change the opacity of the fabric at different points, and multi-material systems allowed them to produce parts with different properties or colors. 

Following these developments, the researchers managed to 3D print a deformable lampshade featuring a ‘dimmer switch,’ that enabled lighting levels to be adjusted by pinching the fabric. In addition, proof-of-concept items such as a shuttlecock and iron-on shirt pocket were later produced, before the team opted to fabricate a full skirt, which gave them an idea. 

Given the high-level of waste that’s endemic in the fashion industry, the scientists concluded that their new process could be used as a way of allowing customers to “try-on” clothes at home. Instead of ordering items to ‘try before they buy,’ the team suggested that tech-savvy clientele could use the DefeXtile method to print out a sample of the material first, preventing items from being returned or thrown away. 

“Clothing ordered online that is returned due to poor fit or misrepresentation on websites is an unnecessary cause of waste in the fashion industry,” stated the researchers. “Due to the widespread use and accessibility of FDM printers, we envision this approach can immediately empower a wide audience with the ability to fabricate fabric into finished forms.”

The researchers’ findings are detailed in their paper titled “DefeXtiles: 3D Printing Quasi-Woven Fabric via Under-Extrusion.” The study was co-authored by Jack Forman, Mustafa Doga Dogan, Hamilton Forsythe and Hiroshi Ishii. 

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Featured image shows the research team’s 3D printed deformable lampshade. Photo via MIT.

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