Researchers from LLNL, Lawrence Livermore National Laboratory adapted a new type of material for its groundbreaking volumetric 3D printing method, which can produce objects almost immediately, thereby greatly expanding the range of material properties that can be achieved with this technology. The results of this research were published in "Advanced Materials" on October 1, and were highlighted in "Nature" magazine.
Volumetric additive manufacturing (VAM) is an emerging method based on photopolymer 3D printing, which can complete complex 3D structures in one step without stacking layer by layer. This method can overcome many shortcomings based on layer-by-layer manufacturing, such as long build time and rough surface. VAM also heralds the broadening of materials available for photopolymer 3D printing, which has fewer constraints on viscosity and reactivity than layered printing. Indeed, although VAM has been proven in extremely soft hydrogels, it has so far been almost entirely dependent on acrylate chemicals.
However, due to the brittleness and glassy nature of the resulting material, acrylate chemical reagents are generally limited. As an alternative method to obtain a wider range of mechanical properties, thermal properties, and optical properties, it is very necessary to introduce alternative cross-linking chemical methods in the field of VAM and wider AM. Thiol alkenyl polymers are a class of materials that have attracted much attention because of their controllable and adjustable mechanical properties. This is usually due to the gradual growth mechanism of the polymerization reaction, and the molecular network in the thiolene material is more uniform.
Thiolene resins are a class of materials suitable for volumetric 3D printing. They can be used with the volumetric additive manufacturing (VAM) technology of LLNL (Lawrence Livermore National Laboratory), including computed axial lithograph (CAL) , This technology creates objects by projecting a three-dimensional patterned beam into a resin vial. When the light cures the liquid resin into a solid at the desired location in the volume, the sample bottle is rotated, and then the uncured resin is drained, leaving the 3D object behind in just a few seconds.
The volumetric 3D printing technology operation steps
① Put the photosensitive resin liquid material in a cup first
②Use DLP light source for volume exposure
③ The turntable drives the cup to rotate
④Cure the resin at the designated position
In the researchers' stereo imaging system, the 3D distribution of light energy is transferred to the resin barrel by superimposing multiple angles of exposure. This method is called CAL (computed axial lithograph). Exposure is a series of projections calculated from a 3D CAD model using a computer tomography (CT) algorithm.
The volumetric 3D printing technology works like a reverse computer tomography (CT) scan. In the CT machine, the X-ray tube rotates around the patient to take pictures of the internal organs of the human body. Then, the computer uses these projections to reconstruct a 3D picture.
In the past, researchers used acrylate-based resins for work, which can produce fragile and fragile objects through the CAL process. However, the new resin chemistry created by carefully balancing three different types has more uses and provides researchers with flexible design molecular space and broader mechanical properties. Using thiolene resin, researchers can use LLNL's custom VAM printer to build tough, strong, stretchable, and flexible objects. These results are a key step towards the vision of using VAM methods to significantly expand the types of materials that can be used for light-driven 3D printing.
The researchers also demonstrated the first example of the method of predicting and measuring the 3D energy dose transferred from the design to the resin to print the article. The method successfully printed the 3D structure in the thiol resin through tomographic volume additive manufacturing. . The researchers said the demonstration provides a general reference for controlled 3D manufacturing and comparison of resin systems.
By studying the behavior of the resin under different light doses, the researchers added that their goal is to improve the consistency between the computational model and the experiment, and apply the photochemical behavior to the computer tomography reconstruction process to generate objects for construction 3D model.
This research represents a “significant advancement in batch additive manufacturing, as they are moving towards the goal of achieving high-performance printing engineering polymers, with particular emphasis on the use of thiol materials in bio-scaffolding. There is hope in applications such as pharmaceuticals, electronic products, and biological materials.