Researchers have developed a groundbreaking high-resolution embedded 3D-printing technique that creates ultra-fine fibers, mimicking the intricate structures found in nature. By employing a solvent exchange process, they achieved unprecedented resolutions of 1.5 microns, paving the way for new bioinspired materials and advanced engineering applications.
Fine hairs and fibers, which are prevalent in the natural world, serve various functions ranging from sensory roles to enhancing the unique consistency of hagfish slime. MechSE Professors Sameh Tawfick and Randy Ewoldt, along with doctoral candidate M. Tanver Hossain and their collaborators, have addressed this challenge with their novel embedded 3D-printing technique, recently published in Nature Communications. Their research delves into the science behind this bioinspired approach to rapidly produce fine fibers in gel.
Unlike traditional 3D-printing methods that layer materials in ambient air, embedded 3D printing deposits materials in a supporting medium, such as hydrogel. In air-based printing, models must be oriented to ensure each layer can support the next, often requiring removable support structures for complex architectures. However, printing in gel eliminates this need, as the gel supports the printed shape, allowing for the efficient creation of complex forms, such as helical springs. Moreover, the printed part can be cured and removed from the gel, which can then be reused for multiple prints.
Despite its advantages, embedded 3D printing has previously struggled to produce very thin features, similar to challenges faced in air-based printing. Filaments with diameters below sixteen microns would often break during the curing process due to surface tension. The research team aimed to create finer diameters that could emulate natural fibers, such as spider silk or the defensive threads extruded by hagfish.
Overcoming Challenges with Solvent Exchange
“There are numerous examples in nature of filamentous structures with diameters of just a few microns,” said Hossain, who is the second author and focused on designing the non-Newtonian gel. “We were determined to make it possible.”
To prevent capillary breakup caused by surface tension, the researchers implemented a solvent exchange method. “We modified both the gel and the printing ink so that the ink would cure immediately upon being deposited into the gel,” Hossain explained. “This instant solidification prevents the filament from snapping.” This innovative approach enabled the team to achieve a remarkable resolution of 1.5 microns. They also explored the use of multiple nozzles for parallel printing, facilitating rapid manufacturing.
First author Dr. Wonsik Eom, now a faculty member in the Department of Fiber Convergence Material Engineering at Dankook University in South Korea, previously worked as a postdoctoral researcher in Tawfick’s lab.
“This research breaks through a long-standing limitation of 3D printing technology—producing soft materials with diameters as small as one micron,” Eom stated, highlighting his role in developing the solvent exchange process. “Achieving such high printing resolution provides a technological foundation for mimicking the microfibers and hair-like structures found in nature, which exhibit extraordinary functionalities.”
The researchers were drawn to embedded 3D printing due to its potential to replicate the properties of hagfish slime, known for its superior mechanical performance due to micron-scale thread bundles. Ewoldt has been studying the mechanics of hagfish slime for over a decade, collaborating with Professor Douglas Fudge from Chapman University.
Implications for Advanced Materials and Engineering
“We adopted embedded 3D printing to replicate these threads,” Eom noted. “Our research has shown that developing high-resolution embedded 3D printing technology allows us to recreate a broader range of natural structures than we initially anticipated.”
“This study aligns with my research group’s vision of enabling novel engineering functionalities by utilizing the complex mechanical behavior of non-Newtonian fluids and soft solids,” Ewoldt commented on his interest in the work. “This perspective bridges foundational areas of mechanics, from fluid mechanics to solid mechanics and everything in between.”
Tawfick emphasized the significance of this method, stating, “It allows us to produce various geometries of hair without being hindered by the downward force of gravity on such fine and flexible structures. This capability enables us to create complex 3D hair with fine diameters using an ultraprecise 3D printer.”
The researchers aim to further advance material development using this technique.
“This method has immense potential, as ultra-fine and long fibers could be combined with functional materials to replicate nature-inspired fibrous structures,” Hossain said.
Eom added, “We are particularly focused on printing fine microstructures that are currently unattainable with conventional semiconductor manufacturing techniques.”
Reference: “Fast 3D printing of fine, continuous, and soft fibers via embedded solvent exchange” by Wonsik Eom, Mohammad Tanver Hossain, Vidush Parasramka, Jeongmin Kim, Ryan W. Y. Siu, Kate A. Sanders, Dakota Piorkowski, Andrew Lowe, Hyun Gi Koh, Michael F. L. De Volder, Douglas S. Fudge, Randy H. Ewoldt, and Sameh H. Tawfick, January 20, 2025, Nature Communications.
