A team of researchers at the University of Texas has created a unique 3D printing method leveraging a special resin that can exhibit both soft and hard material properties. This innovative approach allows printed objects to possess flexible outer layers while maintaining structural integrity in their cores.
The team’s study, titled “Hybrid epoxy-acrylate resins for wavelength-selective multimaterial 3D printing” and published in Nature Materials, drew inspiration from nature’s ability to seamlessly integrate hard and soft materials. According to Zak Page, an assistant professor of chemistry involved in the research, achieving this balance in 3D printing was a significant challenge, but they were able to replicate nature’s precision.
Dual Light Wavelengths for Material Flexibility
The breakthrough comes from utilizing two different wavelengths of ultraviolet (UV) light during the printing process. This is different from conventional methods that typically use a single light color. By switching between violet and more energetic UV light, the resin can be manipulated to harden into a rigid structure or to remain pliable like rubber.
This dual-level hardening ensures that the printed materials can be seamlessly combined without creating weak points. Page explains that the methodology incorporates a molecule with reacting groups to ensure strong bonds at the interfaces between different material states.
To test the resin’s capabilities, the researchers printed an artificial knee joint that successfully exhibited movement without any cracks or wear at the seams. Page noted the resilience of the printed parts: "The soft components were stretchable, while the hard parts maintained the stability expected from commercial plastics."
The technology also holds promise beyond biomedical applications; for instance, they successfully printed electrical switches featuring soft, movable parts integrated with rigid components to prevent breakage.
Interestingly, the research team expressed their surprise at the instant effectiveness of this resin, as it is uncommon for new 3D printing materials to perform as expected right away.
The implications of this technology could extend into various realms, including artificial limbs, flexible electronics, and even innovative consumer products that require both durability and softness.