Engineers 3D print fabric that stiffens on demand - Engineering.com

Oct 17, 2024

3D Printing

Inspired by pangolin scales, RoboFabric has potential applications in medical devices and soft robotics.

Researchers at Nanyang Technological University, Singapore (NTU Singapore), have developed a wearable fabric that is flexible but can stiffen on demand. Created through a combination of geometric design, 3D printing and robotic control, the new technology, RoboFabric, can quickly be made into medical devices or soft robotics, such as limbs for drones.

The NTU research team has developed an elbow support from the versatile material to help people carry heavier loads. They also made a wrist support prototype that could help stabilise joints for daily activities and benefit patients with Parkinson’s disease who experience trembling.

Inspired by the scales of pangolins and armadillos, which interlock to form a protective shell, the first step in making the patent-pending technology is an advanced mathematical algorithm that designs an interlocking system of tiles.

The 3D-printed tiles are then joined together by metal fibres running through tiny channels between them or by an external soft case, which requires negative air pressure or vacuum to be applied constantly.

When the fibres are contracted, the tiles interlock and stiffen, increasing the rigidity of RoboFabric over 350 times and providing additional strength and stability. According to the research team’s findings, published in Advanced Materials, human muscle activity can be reduced by up to 40 per cent when the device assists joints while lifting loads.

“We were inspired by how animals often have multiple functionalities for their limbs through the use of intricate structures, much like the shape-morphing and stiffness-variation in octopuses,” said lead researcher, Professor Wang Yifan from the NTU School of Mechanical and Aerospace Engineering

“We envision that in future, patients who need a plaster cast for fractures would have the option of customising a flexible limb support that is fabric-like before stiffening,” Wang added. “Unlike conventional rigid and unremovable casts, they would also be easy to put on or remove at the touch of a button. In daily use, joint supports can also help the elderly in their daily tasks, helping to reduce the muscle strength needed for heavier loads.”

To customise the joint support, the researchers upload a 3D scan of a wrist or the elbow to proprietary software, through which a special algorithm can automatically dissect a 3D model into dozens of geometric tiles that can be 3D printed in just an hour.

The metal fibres must then be threaded through the holes between the tiles and connected to an electric device that can quickly tighten or loosen the cables. This threading process is currently done by hand, but the team says it could be automated in future, similar to how badminton racquets are re-strung using a machine.

The researchers claim that RoboFabric could also be applied in robotics. In their latest paper, published in Science Robotics, Prof Wang’s team demonstrates a tiny robot made of thin wave-shaped tiles sealed in an elastic envelope. When a vacuum is applied, the RoboFabric transitions to its designated shape and becomes stiff. Conversely, when the vacuum pressure is removed, it relaxes into a soft state.

This actuation of stiffening and softening allows the small robot to climb like a worm or swim in water, carrying small loads or protecting fragile assets by forming a rigid shell around them. These capabilities are important for exploration and rescue robots that need to move in complex terrains and provide protection on demand.

In another demonstration, four such robots are combined to form a robotic gripper on a drone. When made rigid, the soft gripper curls up and can pick up small items, similar to a claw machine. To drop the items, it relaxes. The gripper doubles up as a shock-absorbing pad for hard landings when it curls up. While soft, the grippers can be folded into the drone body and do not affect its flight function.