4D printed metamaterials take shape for morphing wings

Engineers in the US have created 4D printed materials with potential applications in morphing aircraft wings, soft robotics and tiny implantable biomedical devices.

4D printing is based on additive manufacturing technology, but uses special materials and sophisticated designs to print objects that change shape with environmental conditions such as temperature acting as a trigger, said Howon Lee, an assistant professor in the Department of Mechanical and Aerospace Engineering at Rutgers University-New Brunswick. Time is the fourth dimension that allows them to morph into a new shape. The research is published in the journal Materials Horizons.

“We believe this unprecedented interplay of materials science, mechanics and 3D printing will create a new pathway to a wide range of exciting applications that will improve technology, health, safety and quality of life,” said Lee, who is senior author of the paper.

The engineers have created a new class of metamaterials that are engineered to have unusual and counterintuitive properties that are not found in nature.

Previously, the shape and properties of metamaterials were irreversible once they were manufactured. But the Rutgers engineers can tune their plastic-like materials with heat, so they stay rigid when struck or become soft as a sponge to absorb shock.

According to the university, the stiffness can be adjusted more than 100-fold in temperatures between room temperature (73 degrees) and 194 degrees Fahrenheit, allowing control of shock absorption. The materials can be reshaped for a variety of purposes. They can be temporarily transformed into any deformed shape and then returned to their original shape on demand when heated.

The video below – produced by Chen Yang/Rutgers University-New Brunswick – shows how 4D-printed smart materials can morph from stiff to soft and change shape.

It is claimed that the materials could be used in airplane or drone wings that change shape to improve performance, and in lightweight structures that are collapsed for space launches and reformed in space for a larger structure, such as a solar panel.

Soft robots made of soft, flexible and rubbery materials inspired by the octopus could have variable flexibility or stiffness that is tailored to the environment and task at hand. Tiny devices inserted or implanted in people for diagnosis or treatment could be temporarily made soft and flexible for minimally invasive and less painful insertion into the body, Lee said.