Researchers at the University of Texas have achieved a significant breakthrough in 3D printing technology, developing a novel resin-based process that enables the creation of single objects possessing both hard and soft properties. This advanced method, rooted in photopolymerization – the use of light to solidify liquid photo resin – represents a substantial leap forward in fabricating complex structures with varying mechanical characteristics, opening new avenues for biomimetic applications.
The innovation lies in the precise control over material properties. The UT team designed specialized photosystems within the resins that react distinctly to different colors of light. By employing spectral control, specifically ultraviolet and violet light, the printing process can meticulously dictate the hardness or softness of the material at specific points. Lower energy violet light activates a reaction leading to a soft material with fewer molecular connections, while higher energy ultraviolet light triggers a secondary reaction, resulting in a more rigid material with increased connections. A critical challenge in multi-material 3D printing, the weak interface between different monomers, was elegantly resolved by developing a hybrid monomer. This ensures that every polymer incorporates the same hybrid building block, guaranteeing robust integration across transitions from soft to hard regions. The efficacy of this process was demonstrated through proof-of-concept applications published in Nature Materials, including the fabrication of a realistic knee joint complete with integrated ligaments and bones that function cohesively. This pioneering technology holds immense promise for the manufacturing of highly intricate stretchable medical and electronic devices, with vast potential for biomedical applications such such as advanced surgical models and more functional prosthetic devices that closely mimic natural biological structures.
