A new 3D printing technique promises to craft objects using beams of light, aiding all manner of professionals — from zoologists to people aboard spaceships who need to make tools in zero gravity.
The technique, described in a paper published Thursday in the journal Science, involves shining light rays onto a yellow light-sensitive liquid to create solid objects. Here’s how this new technique works: Scientists create a 3D model of the object they desire, create a movie, and use a projector to beam the information into a rotating cylinder. The nature of the liquid means users can encase other objects in resin; creating a screwdriver handle around a piece of metal is one such example.
Hayden Taylor, assistant professor of mechanical engineering at the University of California and senior author of a paper, tells Inverse that this new 3D printing technique uses existing hardware but makes more sophisticated use of its software.
“The apparatus required for the new process is inherently simple: it requires a video projector — which could be a standard off-the shelf projector — and a steadily rotating volume of the light-sensitive material,” Taylor says. The tricky part, he explains, is the calculations used to translate the 3D model into a video — but even that “can be carried out with a personal computer if necessary.”
The printer was designed by looking at computed tomography scans, which are used by doctors to find tumors by sending electromagnetic waves into the body. The team needed to calculate how much light to send and when as the cylinder full resin rotated. As the light hits the resin, photosensitive molecules deplete the dissolved oxygen to create a solid structure. The leftover material is reusable for other projects, and the method creates practically no waste.
It comes at a time when 3D printing is experiencing something of a renaissance, following the mass hype around the area in 2013. The past two months alone, researchers at Columbia University have discovered a way to 3D print wood, another team demonstrated how users can create a whole wedding scene, and researchers at the University of Michigan have created a method that can print objects 100 times faster than before.
Typical 3D printers tend to work like their paper-based counterparts, layering up either ABS plastic or polylactic acid to gradually form objects. This technique, known as fused deposition modeling, tends to produce objects at high speed but low accuracy.
“We do not print layer-by-layer, as is traditional,” Taylor says. “In some other processes, the use of layers risks introducing internal voids or defects and results in a less-than-smooth surface, both of which may reduce strength or make strength highly directional.”
An alternative technique, known as stereolithography, used by the team at the University of Michigan, uses an ultraviolet laser to create an object in resin. It sounds similar to the technique used by Taylor’s team — dubbed computed axial lithography — but there are some interesting differences between techniques in this new era of 3D printing.
“We do not draw the component in a straight line but instead rotate the printing volume relative to the light source,” Taylor says. “This means that we can truly create all points of a 3D object simultaneously rather than sequentially.
“Also, in our process, there is no motion of the printed object relative to the surrounding material during printing. This is an unprecedented aspect of our approach that allows us to print into exceptionally high viscosity materials and eliminates the printing-speed limitations that can be imposed on other processes by fluid flow.”
How This New Technique Might Be Used Aboard Spaceships
The technique could even prove beneficial to astronauts in space. Taylor says that it’s “certainly conceivable that parts made by [computed axial lithography] could be used in space,” adding that “I would speculate that weightlessness could actually be an added benefit for the process.”
The main issue with using CAL on Earth is that the object can sink in the resin as it’s being rendered. The team has designed the resin so that the object doesn’t sink during the printing process by any measurable distance, but working in reduced gravity could make that change even smaller.
If Elon Musk and the like achieve their dream of sending humans to Mars and starting a colony, perhaps they’ll send their explorers out to the red planet with a projector and a giant vat of resin, ready to craft their own tools. At least they’d have something to use for watching movies.
Read the abstract of the paper, titled “Volumetric additive manufacturing via tomographic reconstruction,” below:
Additive manufacturing promises enormous geometrical freedom and the potential to combine materials for complex functions. The speed, geometry, and surface quality limitations of additive processes are linked to the reliance on material layering. We demonstrated concurrent printing of all points within a three-dimensional object by illuminating a rotating volume of photosensitive material with a dynamically evolving light pattern. We print features as small as 0.3 mm in engineering acrylate polymers, as well as printing soft structures with exceptionally smooth surfaces into a gelatin methacrylate hydrogel. Our process enables us to construct components that encase other pre-existing solid objects, allowing for multi-material fabrication. We developed models to describe speed and spatial resolution capabilities. We also demonstrated printing times of 30-120 s for diverse centimeter-scale objects.