While 3D printing still seems like magic for some people, the novelty has worn off for others – but I doubt that’s true for many people regarding 4D printing. 3D printed objects that move or change shape in response to stimulus are still incredible to learn about, and the technology just keeps advancing and becoming capable of creating more complex objects.
Researchers at ETH Zurich have developed 4D printed objects that not only change their shape, but do so in a completely controlled manner that allows the researchers themselves to direct how the material reacts. The objects were developed by Kristina Shea, head of the Engineering Design and Computing Lab at ETH Zurich, and her lab.
“The flat structures we produce do not change their configuration randomly, but rather exactly in the way we design them,” explained Tian Chen, a doctoral student in Shea’s group.
The structures are also capable of bearing weight. The ETH Zurich team is the first to create these kinds of load-bearing 4D printed structures.
The researchers developed an actuating element that stimulates the 4D printed structure to either retract or extend. Those elements were then combined to create more complex structures. As the structures can only take on one of the two states – retracted or extended – at a time, the researchers could predict the structure’s stable three-dimensional form. This also allowed for structures that can take on multiple stable forms. Simulation software created by the researchers enabled them to predict the shapes the structures would take, and the stimulus that needed to be applied to get them to take those shapes.
A multi-material 3D printer was used to print the objects, which were created using two different materials: a rigid polymer that composed most of the structure, and a flexible elastic polymer that made up the moving parts. All of the parts were 3D printed in a single step.
“4D printing has several advantages,” said Shea. “Printing a flat initial form with rigid and elastic sections in a single step is highly efficient. It would be much more complex and time-consuming to produce the three-dimensional object or assemble it from separate components.”
In addition, structures can be transported in flat sheets and then expanded once they reach their destinations. Aerospace is a common application for this type of technology, but the ETH Zurich researchers are also looking into devices such as valves that open and close, or medical stents.
Currently, the researchers are manipulating the structures by hand, but they are working on a technique that will enable the objects to extend in response to temperature. They’re also looking into pneumatic tubing or swelling materials that change shape in response to humidity. The research has been published in a paper entitled “Integrated Design and Simulation of Tunable, Multi-State Structures Fabricated Monolithically with Multi-Material 3D Printing,” which you can access here. Authors include Tian Chen, Jochen Mueller and Kristina Shea. Below, you can see some of the 4D printed structures that the researchers designed:
Discuss in the ETH Zurich forum at 3DPB.com.[Source: ETH Zurich]