Researchers at Duke University have developed a solvent-free polymer for digital light processing (DLP) 3D printing, aimed at enhancing mechanical properties and environmental compatibility, particularly for medical applications.
Published in Angewandte Chemie International Edition, this development marks one of the first solvent-free resins suitable for Digital Light Processing (DLP) 3D printing, eliminating the need for solvent-based dilution in the printing process, according to the researchers. DLP technology uses light to solidify liquid resin into layered structures, commonly used in industrial and dental fields.
However, many polymers suited for DLP printing require a low-viscosity resin, similar to water, to achieve high resolution. To reduce viscosity, traditional methods often use solvents, which can introduce challenges such as up to 30% shrinkage in printed parts and residual stress from solvent evaporation, negatively impacting dimensional accuracy and mechanical strength.
“I wanted to create an inherently thin, low-viscosity material for DLP to use for degradable medical devices,” said Maddiy Segal, a MEMS Ph.D. candidate working in the laboratory of Matthew Becker, the Hugo L. Blomquist Distinguished Professor of Chemistry at Duke. “It took a lot of attempts, but eventually I was able to identify optimal monomers and a synthetic technique to create a solvent-free polymer that can be used in a DLP printer without any dilution.”
Solvent-free material for medical use
Addressing these limitations, the research team created a low-viscosity, solvent-free polymer that eliminates shrinkage and improves strength while retaining degradability within the body.
To develop this material, Segal analyzed the structure and properties of existing resins, systematically adjusting monomers and chain lengths. Using a “guess and check” approach, she experimented with around 60 polymer combinations to achieve the desired low-viscosity characteristics and mechanical properties.
Tests on the solvent-free polymer demonstrated stability in printed parts, which showed no shrinkage or distortion and exhibited greater durability than solvent-based counterparts. These results offer one of the first practical examples of how eliminating solvents in DLP printing can enhance the mechanical properties of degradable polymers.
The primary goal of this work is to advance the use of solvent-free polymers for biodegradable medical implants. Traditional implants, which are not always degradable, often necessitate additional surgeries for removal, creating added strain for patients.
In contrast, devices fabricated from this new polymer could degrade within the body, potentially eliminating the need for follow-up procedures. Beyond medical implants, the material’s biocompatibility and degradability make it suitable for other applications, such as bone adhesives for temporary fracture support and soft robotics, where flexible, degradable materials are essential.
According to Segal, this development is seen as a step towards creating implants that naturally degrade over time, supporting both patient recovery and sustainable practices in medical device production.
Parallel research in bioresorbable materials
Away from Duke University, many studies present a growing movement in 3D printing toward creating patient-friendly, degradable implants that prioritize both healing and sustainability.
Last year, researchers at RWTH Aachen University’s Digital Additive Production facility (DAP) developed a zinc-magnesium (ZnMg) alloy for bioresorbable bone implants as part of the BioStruct project.
Using Laser Beam Powder Bed Fusion (PBF-LB), they created lattice structures tailored to fit specific bone defects, aiming to offer a patient-friendly alternative to treatments like titanium implants, which can strain surrounding bone. The ZnMg alloy showed potential for implants that degrade naturally, reducing the need for additional surgeries.
Back in 2020, researchers at Delft University of Technology developed biodegradable magnesium scaffolds through a solvent-cast 3D printing (SC-3DP) method, showing promise for regenerating large bone defects. Magnesium proved to be a suitable material for orthopedic implants, as it degraded gradually in the body while promoting bone growth, potentially reducing the need for follow-up surgeries.
Using SC-3DP, the researchers created a magnesium-based ink, extruded it into structured layers, and applied a debinding and sintering process to finalize the scaffold. The resulting product featured interconnected pores and enhanced mechanical properties, making it well-suited for bone implants. Future studies were planned to assess the scaffold’s stability, biodegradability, and bone-healing potential in clinical settings.
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Featured image shows a toy boat printed with the new solvent-free resin through digital light processing, demonstrating the details made possible through the new material. Photo via Duke University.
