Using a new technique known as 4D printing,
researchers can print out dynamic 3D structures capable of changing their
shapes over time.
Such 4D-printed items could one day be used in everything from medical implants to home
appliances, scientists added.
Today's 3D
printing creates items from a wide variety of materials — plastic, ceramic,
glass, metal, and even more unusual ingredients such as chocolate and living cells. The machines work by setting down layers of material just like ordinary
printers lay down ink, except 3D printers can also deposit flat layers on top
of each other to build 3D objects.
"Today,
this technology can be found not just in industry, but [also] in households for
less than $1,000," said lead study author Dan Raviv, a mathematician at
MIT. "Knowing you can print almost anything, not just 2D paper, opens a
window to unlimited opportunities, where toys, household appliances and tools
can be ordered online and manufactured in our living rooms."
Now, in a
further step, Raviv and his colleagues are developing 4D printing, which
involves 3D printing items that are designed to change shape after they are
printed.
"The most
exciting part is the numerous applications that can emerge from this
work," Raviv told Live Science. "This is not just a cool project or
an interesting solution, but something that can change the lives of many."
In a report
published online today (Dec. 18) in the journal Scientific Reports, the researchers
explain how they printed 3D structures using two materials with different
properties. One material was a stiff plastic, and stayed rigid, while the other
was water absorbent, and could double in volume when submerged in water. The
precise formula of this water-absorbent material, developed by 3D-printing company Stratasys in Eden Prairie, Minnesota, remains a secret.
The researchers
printed up a square grid, measuring about 15 inches (38 centimeters) on each
side. When they placed the grid in water, they found that the water-absorbent
material could act like joints that stretch and fold, producing a broad range
of shapes with complex geometries. For example, the researchers created a
3D-printed shape that resembled the initials "MIT" that could
transform into another shape resembling the initials "SAL."
"In the
future, we imagine a wide range of applications," Raviv said. These could
include appliances that can adapt to heat and improve functionality or comfort,
childcare products that can react to humidity or temperature, and clothing and footwear
that will perform better by sensing
the environment, he said.
In addition,
4D-printed objects could lead to novel medical implants. "Today,
researchers are printing biocompatible parts to be implanted in our body,"
Raviv said. "We can now generate structures that will change shape and
functionality without external intervention."
One key
health-care application might be cardiac stents, tubes placed inside the heart
to aid healing. "We want to print parts that can survive a lifetime inside
the body if necessary," Raviv said.
The researchers
now want to create both larger and smaller 4D-printed objects. "Currently,
we've made items a few centimeters in size," Raviv said. "For things
that go inside the body, we want to go 10 to 100 times smaller. For home
appliances, we want to go 10 times larger."
Raviv cautioned
that a great deal of research is needed to improve the materials used in 4D
printing. For instance, although the 4D-printed objects the researchers
developed can withstand a few cycles of wetting and drying, after several dozen
cycles of folding and unfolding, the materials lose their ability to change
shape. The scientists said they would also like to develop materials that
respond to factors other than water, such as heat and light.
