Researchers at the University of Illinois Urbana-Champaign have developed an advanced 3D printing method that enables the production of fine, continuous and soft fibers. The technique, published in the journal Nature Communications, is based on an embedded solvent-exchange 3D printing process.
Traditional 3D printing processes build up materials layer by layer in the air, which leads to instabilities when producing filaments with diameters of less than 16 micrometers. These fine structures often break due to surface tension before they can harden. The new process avoids this problem by embedding the material in a support medium such as hydrogel. This medium stabilizes the printed structures during curing and enables the production of complex shapes without additional support structures.
“In nature, there are many examples of filamentous structures that achieve a diameter of only a few microns,” said doctoral candidate M. Tanver Hossain, who is the second author and focused on designing the non-Newtonian gel. “We knew it had to be possible.”
“This research overcomes a long-standing limitation of 3D printing technology—printing soft materials with a diameter as small as one micron,” said Dr. Wonsik Eom, now a faculty member in the Department of Fiber Convergence Material Engineering at Dankook University in South Korea. “Achieving such high printing resolution means we now have the technological foundation to mimic the microfibers and hair-like structures found in nature, which exhibit remarkable functionalities.”
A central element of this method is solvent replacement. The printing material is modified in such a way that it hardens immediately on contact with the gel. This prevents the filaments from tearing due to almost immediate solidification. With this approach, the researchers were able to achieve a resolution of 1.5 micrometers. In addition, the use of several printing nozzles in parallel enables the fibers to be produced quickly.
The inspiration for this development comes from nature, in particular from filamentous structures such as spider silk or the slimy defensive threads of hagfish. These natural fibres are characterized by remarkable mechanical properties that can be imitated by the new printing technology.
“This study relates to the broader research vision of my group—to enable novel engineering functionality by using the complex mechanical behavior of non-Newtonian fluids and soft solids,” Professor Randy Ewoldt, one of the lead researchers, said. “This perspective integrates across foundational areas of mechanics, from fluid mechanics to solid mechanics and behavior in-between.”
The potential applications of this technology are diverse. They range from the replication of biological structures for medical purposes to the development of new materials with customized properties. With the ability to efficiently produce fine and flexible fibers, this method opens up new possibilities in areas such as biomedicine, the textile industry and materials science.
“The significance of this method is to produce many geometries of hairs while not having to deal with the downward force of gravity on such fine and flexible hair,” said MechSE Professor Sameh Tawfick, who has worked to showcase the method’s usefulness and various applications. “This allows us to produce complex 3D hair, having fine diameters, using an ultraprecise 3D printer.”
Overall, this innovative 3D printing technique represents a significant advance that allows the complex structures and functions of natural fibers to be replicated and harnessed for technological applications.
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