Stanford University
Kyiv’s Saint Sophia Cathedral in the blue and yellow of the Ukrainian flag, printed using the iCLIP method
Advancements in 3D printing have made it easier for designers and engineers to customise projects, create physical prototypes at different scales, and produce strictures that can’t be made with more traditional manufacturing techniques.
However, the technology still has certain limitations, such as speed and only being able to use one material at a time.
Researchers at Stanford University have developed a method of 3D printing that the team says will create prints faster, using multiple types of resin in a single object. The researchers claim the design is five to ten times faster than the quickest high-resolution printing method currently available, and could potentially allow researchers to use thicker resins with better mechanical and electrical properties.
“This new technology will help to fully realise the potential of 3D printing,” said Joseph DeSimone, the Sanjiv Sam Gambhir Professor in Translational Medicine and Professor of Radiology and of Chemical Engineering at Stanford and corresponding author on the paper. “It will allow us to print much faster, helping to usher in a new era of digital manufacturing, as well as to enable the fabrication of complex, multi-material objects in a single step.”
In 2015, a team that included DeSimone created a method of 3D printing called Continuous Liquid Interface Production, or CLIP. This method features a rising platform smoothly pulling the object, seemingly fully formed, from a thin pool of resin. The resin at the surface is hardened into the right shape by a sequence of UV images projected through the pool, while a layer of oxygen prevents curing at the bottom of the pool and creates a “dead zone” where the resin remains in liquid form. This process was commercialised by Carbon, who, led for its first few years by DeSimone, has gone on to become one of the leading names in additive manufacturing, with the likes of Adidas, Riddell and Ford applying the technology.
The researchers on the new project say that the new design improves on the method brought to market by Carbon back in 2015.
The dead zone is the key to CLIP’s speed. As the solid piece rises, the liquid resin is supposed to fill in behind it, allowing for smooth continuous printing. Issues can arise if the piece rises too quickly, or the resin is particularly viscous. The new method is called injection CLIP, or iCLIP, where the researchers have mounted syringe pumps on top of the rising platform to add additional resin at key points.
“The resin flow is a very passive process, you’re just pulling the object up and hoping that suction can bring material to the area where it’s needed,” said Gabriel Lipkowitz, a PhD student in mechanical engineering at Stanford and lead author on the paper. “With this new technology, we actively inject resin onto the areas of the printer where its needed.”
Through injecting additional resin separately, iCLIP presents the opportunity to print with multiple types of resin over the course of the printing process, with each new resin requiring its own syringe. The researchers tested the printer with three different syringes, each filled with a resin dyed a different colour.
Models of famous buildings from several countries in the colour of each country’s flag were successfully printed. This included Saint Sophia Cathedral in the blue and yellow of Ukraine, and Independence Hall in the American red, white and blue.
Lipkowitz added: “The applications range from very efficient energy-absorbing structures to objects with different optical properties and advanced sensors.”
“A designer shouldn’t have to understand fluid dynamics to print an object extremely quickly,” said Lipkowitz. “We’re trying to create efficient software that can take a part that a designer wants to print and automatically generate not only the distribution network, but also determine the flow rates to administer different resins to achieve a multi-material goal.”
The work was funded by the Precourt Institute for Energy at Stanford, the Stanford Woods Institute for the Environment, and the National Science Foundation.
In 2017, 3D printing played a key role in malaria testing at Stanford University, when researchers produced a very cheap centrifuge.