A team from the École Polytechnique Fédérale de Lausanne (EPFL) has achieved a significant advancement in 3D printing technology, specifically through a method known as tomographic volumetric additive manufacturing (TVAM). This innovative approach enables the rapid creation of entire three-dimensional objects using light, bringing researchers closer to fabricating large, tissue-like structures that could have medical applications for repairing human tissues.
Traditional 3D printers construct objects layer by layer, which can be time-consuming and less efficient. In contrast, TVAM uses a rotating vial of liquid resin, where lasers selectively harden the material to create complete structures almost instantaneously. Previous versions of this technology faced energy efficiency issues, wasting much of the laser power. However, the EPFL team has improved efficiency significantly by controlling the alignment of light waves instead of merely adjusting brightness, resulting in a system that is approximately 70 times more efficient.
The innovation involves replacing older digital micromirror devices with phase light modulators (PLMs), which alter the phase of light waves instead of just turning them on and off. This modification allows for better organization and direction of light, leading to increased laser power effective in the printing process. As a result, the system achieved about 24% absolute efficiency, a notable enhancement over previous methods.
The researchers reported impressive printing speeds, able to produce millimeter-scale objects in seconds and centimeter-scale objects in minutes. For instance, they printed a fusilli-shaped object in just 32 seconds with low power, showcasing the system’s capacity for creating intricate designs quickly.
Additionally, they tackled a common issue in holographic printing called speckle—grainy patterns caused by laser interference—by implementing a technique known as time multiplexing. This method involved projecting multiple holograms in rapid succession, which allowed the resulting prints to achieve smoother surfaces and fewer defects.
One of the most exciting findings from their research was the successful integration of living cells into the printed structures. The team designed multiacinar structures mimicking parts of the pancreas using gelatin-based hydrogels embedded with human fibroblast cells. Remarkably, the printed structures maintained the viability of these cells, demonstrating the potential for bioprinting applications.
The researchers also utilized "self-healing" Bessel beams that maintain focus over longer distances, further improving accuracy throughout the entire volume of resin, even when faced with scattering caused by embedded cells.
This groundbreaking work represents a significant stride toward practical medical applications of bioprinting, with the potential to create custom implants and engineered tissues directly from living materials. Notably, the method reduces energy demands and print times, addressing significant challenges in current tissue engineering practices, which often face limitations regarding size, duration, and cellular damage.
Future developments may focus on enhancing projection fidelity, understanding the behavior of dense living bioresins during printing, and eliminating the need for rotating resin, making the printing process even more efficient. Ultimately, this advancement could revolutionize regenerative medicine and advanced manufacturing, opening new possibilities for the production of customized medical implants and advanced industrial components.
Research findings are available in the journal Light Science & Applications.
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