Researchers have developed a new method for 3D printing objects with very different properties, including levels of hardness and transparency, on a pixel-by-pixel basis while using commonly available materials and inexpensive 3D printers. The method, described today in the journal Science by researchers from The University of Texas at Austin, Sandia National Laboratories and two other national laboratories, could lend itself to the creation of realistic models of body parts for medical students to practice surgery on or new types of personal protective gear.
"We can control molecular level order in three-dimensional space, and in doing so, completely change the mechanical and optical properties of a material," said Zak Page, a UT associate professor of chemistry and author on the paper. "And we can do that all from a really simple, inexpensive feedstock by just changing the light intensity. It's the simplicity at the heart of it that's really exciting."
The new 3D printing method, called Crystallinity Regulation in Additive Fabrication of Thermoplastics (CRAFT), uses a commercial printer with varying patterns of light to transform a widely available liquid resin called cyclooctene into a solid plastic object. The process involves projecting a series of grayscale images onto a platform that moves up and down in the liquid, building the object up from a series of microscopically thin 2D layers of polymeric material.
Funding for this work was provided by the U.S. Department of Energy, the National Science Foundation and the Robert A. Welch Foundation.
One potential application of the method is creating models of the human body for use by medical students. CRAFT can simulate complex interconnected structures of different types of material from bone to ligament to muscle. Previously, 3D-printed models have not been a realistic alternative to cadavers, which medical schools must continuously secure, often at a high expense and amid difficulties. Existing methods for printing models involve expensive ink jet printers and combine materials that don't adhere well to each other, causing failures at the interfaces that don't reflect what would happen naturally with human tissue. CRAFT yields models without these drawbacks.
Energy damping, such as for sound proofing or for personal protective gear like helmets or armor, is another potential CRAFT application. Page envisions developing "bioinspired materials"—with internal structures that alternate hard and soft regions, the way that nature does in structures like tree bark and bones, allowing for the absorption of vibrations and impacts without breaking.
Page has previously developed other new methods for 3D printing that enable spatial control over stiffness and strength, but with more complex resin components and custom equipment. He also says objects made with CRAFT, while not fully recyclable, might still potentially reduce waste, as they can easily be melted down or dissolved with a solvent and recast into a new form or shape.
"DLP or LCD 3D printing, which this method is compatible with, are some of the cheapest printers that you can buy," Page said. "You can get one of these printers with the capability to do grayscale projection for $1,000 or less and be off to the races printing."
The work was led by Alex Commisso and Samuel Leguizamon, both formerly at Sandia National Laboratories. Leguizamon is now a scientist at Savannah River National Laboratory and Commisso is a materials chemist at Azul 3D.
