Stanford engineers have developed a new material for nanoscale 3D printing that can absorb twice as much energy as other materials of similar density and can be used to create better security network lighting.
Science fiction is responsible for a fast 3D printing process that can quickly create new things from any number of materials. But in reality, 3D printing is still limited in features and types of materials that can be used, especially when printing on small objects.
Stanford researchers have developed a new material for nanoscale 3D printing – creating materials that are only a fraction of the width of a human hair – and use it to print small lattices with both strength and light. In an article published in Science, the researchers showed that the new material can absorb twice as much energy as other 3D printed materials of similar density. In the future, their inventions can be used to create lightweight protection for vulnerable parts of satellites, drones and microelectronics.
“There’s a lot of interest right now in 3D modeling for mechanical engineering,” said Wendy Gu, assistant professor of mechanical engineering and corresponding author. “What we did on top of that was create a material that resists forces well, so it is not only a 3D structure, but also a material that provides good protection.”
Characterization of metal nanoclusters
To design a better material for 3D printing, Gu and his colleagues introduced metal nanoclusters — tiny packs of atoms — into their printing process. The researchers are printing a process known as double photo lithography, where the printed material is hardened by a chemical reaction initiated by laser light. They found that their nanoclusters were very good at initiating this reaction and used a polymer composite material printed on metal.
“Nanoclusters have excellent properties for absorbing laser light and converting it into chemical reactions,” says Gu. “And they’re able to do that with multiple polymer classes, so they’re doing better than I expected.”
The researchers were able to combine metal nanoclusters with acrylates, epoxides and proteins – several classes of polymers used in 3D printing. Also, nanoclusters helped speed up the printing process. By combining nanoclusters with proteins, for example, Gu and his colleagues can print at a speed of 100 millimeters per second, which is about 100 times faster than what was previously achieved with nanometric protein printing scale.
The researchers tested their new material with several different lattice structures, confirming the ability to carry heavy loads in some and the ability to absorb impact in others. With the nanocluster-polymer composite, the whole structure showed a great combination of energy absorption, strength and recovery – basically the ability to fall and return.
“The design of the truss is really important, but what we’re showing here is that if the material is optimized, that’s important for performance,” Gu says. “You don’t have to worry about the shape of 3D if you have the right materials to print it.”
Copy the natural world
In a way, Gu and his colleagues are trying to copy what creation has already done. Bone, for example, derives its strength from a combination of hard exteriors, nanoscale porosity, and small soft materials. This combination of 3D structure and many well-designed materials allows our bones to transmit energy without breaking (most of the time) while being smaller. Ideally, a 3D-printed storage building would also contain a variety of materials, some hard and some soft, to better absorb impact and resist crushing.
“Since the nanoclusters can react with these different chemicals, we can use them to print many things in one design,” Gu says. “That’s something we’d like to pursue.”
