Taking inspiration from some of the unique attributes of dragonfly wings, scientists at Germany’s Kiel University have developed a new type of splint for injured joints that offers support in all the right places. The device can withstand loads many times its own weight without restricting bodily movement, hitting what its creators see as a sweet spot for the support of injured joints.
The new medical device is designed for musculoskeletal injuries, which account for a large portion of sporting injuries and result from sprains, strains or overloading of the joints. In the eyes of the Kiel University team, conventional splints used for these types of injuries either restrict the user’s mobility or don’t provide the support the joint needs, and they believe they've found a better solution inspired by nature.
As part of their wider research, the team was investigating the way dragonfly wings are able to endure wind currents of varying strengths and even crashes with solid objects. This requires them to be both stable and mobile, which the researchers say in engineering are generally mutually exclusive, but occur often in tandem in nature.
“In the case of dragonflies, the key is the joint-like connections in their wings,” explains study author Professor Stanislav Gorb. “They are interwoven with patches of the elastic protein resilin, which initially allow great freedom of movement. However, if a certain angle of extension is exceeded, stiff cuticular spikes on the wing block a further movement by interlocking. They now support the joint and give wings the required stability to withstand high loads.”
The scientists recreated this mechanism in a special hinge made from polylactic acid (PLA) that weights just 23 g (0.8 oz). The plastic hinge can be integrated with elastic textile wraps to adhere to joints and has no impact on movement, until they hit an angle of 70 degrees, in which case inbuilt spikes block the movement and stabilize the joint, just like in the dragonfly wings.
"The tests showed that our splint has a load-bearing capacity of about 320 Newton that means around 32 kilograms (70.5 lb) which is more than 1,300 times of the splint’s own weight,” says Ali Khaheshi, the first author of the study. “If the structure is made of stronger materials than PLA, it could withstand loads up to 450 kg (992 lb) which would be much higher than the force experienced by the world record of weightlifting.”
The device can be 3D printed, meaning that it can be produced easily and cheaply, and can be adapted for use on hands, knees and elbows. The team says its function can also be modified, so it could be made to bend a certain amount for a rehab patient recovering from a certain injury, for example, and can also be made to easily switch between mobile mode and support mode. The team is now looking for industry partners to help bring the device to market.
The research was published in the journal Applied Physics, while the video below provides an overview of the research.
Source: Kiel University