September 21, 2015

4-D Technology Allows Self-folding of Complex Objects

This image shows the folded box, which is intended to simulate a postal mailer.
The folding is done in a tank of warm water to provide uniform heating to the materials.
(Credit: Qi Laboratory)

(September 21, 2015) Using components made from smart shape-memory materials with slightly different responses to heat, researchers have demonstrated a four-dimensional printing technology that allowed creation of complex self-folding structures.

The technology, developed by researchers at the Georgia Institute of Technology and the Singapore University of Technology and Design (SUTD), could be used to create 3-D structures that sequentially fold themselves from components that had been flat or rolled into a tube for shipment. The components 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, toys and range of other structures.

The researchers used smart shape memory polymers (SMPs) with the ability to remember one shape and change to another programmed shape when uniform heat is applied. The ability to create objects that change shape in a controlled sequence over time is enabled by printing multiple materials with different dynamic mechanical properties in prescribed patterns throughout the 3-D object. When these components are then heated, each SMP responds at a different rate to change its shape, depending on its own internal clock. By carefully timing these changes, 3-D objects can be programmed to self-assemble.

Yiqi Mao, a postdoctoral fellow in the laboratory of Professor Jerry Qi at Georgia Tech, shows a
folded box structure produced from smart shape-memory materials. The materials were
created with the 3-D printer shown with him. (Credit: Candler Hobbs, Georgia Tech)

The research was reported September 8 in the journal Scientific Reports, which is published by Nature Publishing. The work is funded by the U.S. Air Force Office of Scientific Research, the U.S. National Science Foundation and the Singapore National Research Foundation through the SUTD DManD Centre.

This image shows the self-folding process of smart shape-memory materials with slightly
different responses to heat. Using materials that fold at slightly different rates is
important to ensure that the components do not interfere with one another during
the process. (Credit: Qi Laboratory)

The research creates self-folding structures from 3-D printed patterns containing varying amounts of different smart shape-memory polymers. The patterning, done with a 3-D printer, allows the resulting flat components to have varying temporal response to the same stimuli. Earlier methods required application of differential heating at specific locations in the flat structure to stimulate the shape changes.

Using a 3-D printer, researchers produce smart shape-memory materials with
slightly different responses to heat. Heat from water in a tank activates the
materials and begins the self-folding process.
(Credit: Qi Laboratory, Georgia Tech)

“Previous efforts to create sequential shape changing components involved placing multiple heaters at specific regions in a component and then controlling the on-and-off time of individual heaters,” explained Jerry Qi, a professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech. “This earlier approach essentially requires controlling the heat applied throughout the component in both space and time and is complicated. We turned this approach around and used a spatially uniform temperature which is easier to apply and then exploited the ability of different materials to internally control their rate of shape change through their molecular design.”

journal reference (Open Access) >>