NTU Singapore develops 3D-printed active tissue for medical devices and soft robotics

Researchers at Nanyang Technological University, Singapore (NTU Singapore), have developed an innovative wearable fabric that is flexible but can stiffen when needed. The new technology, RoboFabric, was developed through a combination of geometric design, 3D printing and robotic control and can be quickly fabricated into medical devices or soft robots, such as limbs for drones.

The NTU team has already developed an elbow brace made from RoboFabric to help people carry heavy loads. A prototype wrist support has also been produced that could stabilize joints during everyday activities and benefit patients with Parkinson’s disease who suffer from tremors. Inspired by the scales of pangolins and armadillos, which interlock to form a protective shell, the patented technology is based on a mathematical algorithm that designs a system of interlocking tiles.

The tiles are 3D printed and connected by metal fibers that run through tiny channels between them or through an outer soft shell that requires constant negative pressure. When the fibers contract, the tiles interlock and increase the stiffness of the RoboFabric by 350 times, providing additional strength and stability. According to research published in the journal Advanced Materials, human muscle activity can be reduced by up to 40 percent when the device supports the joints during lifting.

Lead scientist, Nanyang Assistant Professor Wang Yifan from the NTU School of Mechanical and Aerospace Engineering, said, “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.”

He added that future patients with fractures could have the option of using flexible limb supports that harden at the touch of a button, as opposed to conventional rigid and non-removable casts.

To customize the joint support, a 3D scan of the wrist or elbow is uploaded to special software that automatically breaks down a 3D model into dozens of geometric tiles that can be printed in as little as an hour. The metal fibers are then manually threaded through the holes between the tiles and connected to an electrical device that can quickly tighten or loosen the cables. This threading work could be automated in the future, similar to how badminton rackets are strung by machines.

Adjunct Associate Professor Loh Yong Joo, Head of the Department of Rehabilitation Medicine at Tan Tock Seng Hospital, commented on the technology:  “This technology could be potentially useful in several cases, such as individuals with joint injuries, as it could allow safe adjustment of movement range during recovery. For those with upper limb motor weakness, such as post-stroke patients, RoboFabric could provide support to perform some functional tasks.

Additionally, individuals with movement disorders like Parkinson’s disease may benefit from the stability RoboFabric offers, which stabilises the movement trajectory to complete functional tasks safely. If adapted for knee applications in future, it may even serve as a stabilising orthosis to improve gait patterns and help prevent falls.”

In addition to medical applications, RoboFabric could also be used in robotics. In the journal “Science Robotics”, the team describes a small robot made of wave-shaped tiles that stiffens itself through negative pressure and can therefore climb like a worm or swim in water. Four such robots can be combined to form a gripper on a drone that can pick up and place small objects.

The team is currently looking for industrial partners for application tests in the fields of healthcare and robotics. The project was supported by the Singapore Agency for Science, Technology and Research (A*STAR).