A team of researchers from the Georgia Institute of Technology (Georgia Tech; Atlanta, GA) and colleagues has developed a new 3D printing method to create objects that can permanently transform into a range of different shapes in response to heat. The team, which included researchers from the Singapore University of Technology and Design (SUTD) and Xi'an Jiaotong University (China), created the objects by printing layers of shape memory polymers, with each layer designed to respond differently when exposed to heat.
"This new approach significantly simplifies and increases the potential of 4D printing by incorporating the mechanical programming post-processing step directly into the 3D printing process," says Jerry Qi, a professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech. "This allows high-resolution 3D-printed components to be designed by computer simulation, 3D printed, and then directly and rapidly transformed into new permanent configurations by simply heating."
Their development of the new 3D-printed objects follows earlier work the team had done using smart shape memory polymers (SMPs), which have the ability to remember one shape and change to another programmed shape when uniform heat is applied, to make objects that could fold themselves along hinges. "The approach can achieve printing time and material savings up to 90%, while completely eliminating time-consuming mechanical programming from the design and manufacturing workflow," Qi says.
"Our composite materials at room temperature have one material that is soft but can be programmed to contain internal stress, while the other material is stiff," says Zhen Ding, a postdoc researcher at SUTD. "We use computational simulations to design composite components where the stiff material has a shape and size that prevents the release of the programmed internal stress from the soft material after 3D printing. Upon heating, the stiff material softens and allows the soft material to release its stress and this results in a change—often dramatic—in the product shape."
The new 4D objects could enable a range of new product features, such as allowing products that could be stacked flat or rolled for shipping and then expanded once in use, the researchers say. Eventually, the technology could enable components that could respond to stimuli such as temperature, moisture, or light in a way that is precisely timed to create space structures, deployable medical devices, robots, and toys.
Full details of the work appear in the journal Science Advances; for more information, please visit http://dx.doi.org/10.1126/sciadv.1602890.
