Researchers have developed a groundbreaking solvent-free polymer designed for digital light printing (DLP), a method of 3D printing that gradually constructs solid objects from a thin layer of resin. This innovation not only addresses a common problem of shrinkage in finished products but also enhances the mechanical properties of the printed items while ensuring they can still degrade safely in the body.
Additive manufacturing (AM) has transformed numerous sectors and promises to impact even more in the near future. While many are familiar with 3D printers similar to inkjet models, there is another AM technique that offers unique benefits by building objects layer by layer using light.
One prominent example is digital light processing (DLP), which is extensively used in both industrial settings and dental practices. DLP technology converts a liquid resin into solid components by utilizing light, effectively pulling objects from a shallow resin pool layer by layer.
However, a significant challenge with this 3D printing technique is that the resins must possess low viscosity to operate effectively at high resolutions. Many useful polymers for DLP printing are solid or too thick, necessitating solvents to dilute them to the right viscosity.
Unfortunately, incorporating these solvents can introduce serious issues, such as significant shrinkage (up to 30%) and poor dimensional accuracy post-printing, due to residual stress caused by solvent evaporation.
In a study published online on August 30 in Angewandte Chemie International Edition, a team of researchers from Duke University introduced a new polymer for DLP printing that does not require solvents. This innovation not only resolves the shrinkage issue, but also enhances the mechanical strength of the parts while ensuring they are still biodegradable.
Maddiy Segal, a PhD candidate specializing in MEMS and working in Matthew Becker’s chemistry lab at Duke, stated, “I aimed to develop an inherently thin, low-viscosity material for DLP suitable for degradable medical devices.” After numerous attempts, she successfully identified the right monomers and a synthetic method to create a polymer that could be utilized in DLP printers without requiring dilution.
Being among the first to create a solvent-free resin suitable for DLP, Segal was eager to test the properties of parts made from it. She found that the test components did not shrink or change shape at all, and overall, they exhibited greater strength and durability compared to those produced with solvents. Her results represent one of the first empirical validations of improved mechanical properties due to the absence of solvents in the DLP 3D printing of degradable polymers.
To develop her new polymer, Segal examined the structures and properties of existing resins from the Becker Lab and others, systematically modifying the monomers and chain lengths to achieve the desired low-viscosity characteristics. Her approach involved a method of trial and error, where she adjusted the polymer’s ingredients or “recipes” until she found the right combination.
The process is somewhat akin to cooking; it requires mixing different ingredients, applying heat, and testing the results until the desired outcome is reached. Over the course of her research, Segal experimented with approximately 60 different combinations before successfully creating the product she envisioned.
Segal’s overarching aim is to use this method for crafting biodegradable medical implants. Currently, many temporary medical implants are non-degradable, necessitating multiple surgeries for both implantation and removal. Through her work, Segal aspires to devise implants that can dissolve through the body’s natural processes.
Devices made from this innovative material could be implanted with the expectation that they will degrade over time, thus eliminating the need for follow-up surgeries to extract them. Furthermore, it might also be utilized as a bone adhesive for temporarily holding fractures together or in soft robotics, where a flexible and degradable material is crucial.
“This type of material is central to my work’s main objective,” Segal explained. “In reality, this technique could be applied to any implant that is intended to be biodegradable over time, rather than remaining indefinitely in the body.”
This research receives support from the National Institutes of Health (1R01HL159954-01). Duke University has also filed a provisional patent application for this technology (Application #63544353).
