I’m probably dating myself here, but do you remember the scene from Crocodile Dundee, where Paul Hogan’s character, a croc hunter who travels to New York City following the lure of a lovely lady, and is mugged at knifepoint? (If you don’t recall it, YouTube to the rescue: https://youtu.be/WWl8EbNN8NM). Staring down that switchblade, Mick Dundee is surprised when his date suggests they hand over their wallets as ordered. “Mick…he’s got a knife,” she says warningly. Mick chuckles and says knowingly, “That’s not a knife.” Pulling his own — a modified Bowie knife (created exclusively for the movie) that resembles a small sword — from his pocket, he explains, “That’s a knife.”
The scene immediately sprang to mind as I worked on this issue — and not only because I like badly dated movies from the 1980s. Not long after I finished editing our cover story, “3D Printing: All About the Heat,” a press release about 4D printed materials landed in my box. Not unlike Crocodile Dundee though, rather than scare me off, news of the advancements in 4D technologies made me even more excited to share our article on additive printing with you.
In the article, Emma Pollack of Powerblanket notes that 3D printers are already being used to produce myriad products: toys, medical devices and instruments among them. Pollack provides a thorough overview of fused deposition modeling, which is sometimes called fused filament fabrication. Key components of a 3D printer involve familiar thermal processing equipment — nozzle heater in the extruder as well as a heater in the print bed, plus temperature sensors and fans to provide controlled cooling. And, like many other thermal processes, non-ideal temperatures are often at the root of many manufacturing defects and failures. As materials and printing technology develop, what is possible with 3D printing is likely to expand in many directions.
“While some limitations in technology prevent printing at certain sizes and with certain materials, research and development is advancing the capabilities quickly,” Pollack notes. Those limitations are some of the reasons 4D printing research is occurring.
Researchers at Rutgers University–New Brunswick have created smart materials that can morph from solid to flexible — and change shape. The 4D objects are printed similarly to 3D projects with one important caveat: special materials and sophisticated designs are used to print objects that change shape with environmental conditions such as a change in temperature. “Time is the fourth dimension that allows them to morph into a new shape,” says Howon Lee, an assistant professor in the department of mechanical and aerospace engineering and the senior author on a paper about the Rutgers research.
According to a university report, the engineers created a new class of “metamaterials” — materials engineered to have unusual and counterintuitive properties that are not found in nature. “Previously, the shape and properties of metamaterials were irreversible once they were manufactured. But the Rutgers engineers can tune their plastic-like materials with heat, so they stay rigid when struck or become soft as a sponge to absorb shock.” The behavior of the objects produced is adjustable over the more than 100°F range of the metamaterials.
With equipment developments and exciting new materials for 3D and 4D printing on the horizon, perhaps one day soon we can even remanufacture that poor mugger’s ruined, red leather jacket as the latest fashion look. They say fashion trends recycle, and who wouldn’t want to return to the era of parachute pants and all-pleather outfits?