The new technique can be used to create a variety of objects, such as cubes or pyramids, without ever having to physically touch the material. Image: North Carolina State University |
Researchers from North
Carolina State University have developed a simple way to
convert 2D patterns into 3D objects using only light.
“This is a novel application of existing materials, and has potential for
rapid, high-volume manufacturing processes or packaging applications,” says Michael
Dickey, an assistant professor of chemical and biomolecular engineering at NC
State and co-author of a paper describing the research.
The process is remarkably simple. Researchers take a pre-stressed plastic
sheet and run it through a conventional inkjet printer to print bold black
lines on the material. The material is then cut into a desired pattern and
placed under an infrared light, such as a heat lamp. A video demonstration can be seen here.
The bold black lines absorb more energy than the rest of the material, causing
the plastic to contract—creating a hinge that folds the sheets into 3D shapes.
This technique can be used to create a variety of objects, such as cubes or
pyramids, without ever having to physically touch the material. The technique
is compatible with commercial printing techniques, such as screen printing,
roll-to-roll printing, and inkjet printing, that are inexpensive and high-throughput
but inherently two dimensional.
By varying the width of the black lines, or hinges, researchers are able to
change how far each hinge folds. For example, they can create a hinge that
folds 90 degrees for a cube, or a hinge that folds 120 degrees for a pyramid.
The wider the hinge, the further it folds. Wider hinges also fold faster,
because there is more surface area to absorb energy.
“You can also pattern the lines on either side of the material,” Dickey
says, “which causes the hinges to fold in different directions. This allows you
to create more complex structures.”
The researchers developed a computer-based model to explain how the process
works. There were two key findings. First, the surface temperature of the hinge
must exceed the glass transition temperature of the material, which is the
point at which the material begins to soften. Second, the heat has to be
localized to the hinge in order to have fast and effective folding. If all of
the material is heated to the glass transition temperature, no folding will
occur.
“This finding stems from work we were doing on shape memory polymers, in
part to satisfy our own curiosity. As it turns out, it works incredibly well,”
Dickey says.
The paper, “Self-folding of polymer sheets using local light absorption,”
was published in Soft Matter.
