This 3D-printed bionic hand moves closer to the real thing with ‘thermal training’

When it comes to bionic limbs, one of the main problems with their form and function is that they look and feel … well, bionic. Despite the incredible advances in medicine and technology that have allowed prosthetics to behave more like organic body parts and even offer sensation, the fact remains that they don’t behave (or look) quite like the real thing. But now, Dr. Erik Engeberg, an assistant professor in the Department of Ocean and Mechanical Engineering at Florida Atlantic University, may have a solution to this problem with his development of a “novel robotic finger that looks and feels like the real thing.” Drawing from nature and biology for his design, Engeberg employed “shape memory alloy (SMA), a 3D CAD model of a human finger, a 3D printer, and a unique thermal training technique” in order to create a 3D-printed bionic finger that may take prosthetics into a whole new generation.

Whereas prosthetics and bionic limbs are historically rather immobile, or at the very least, rigid, Engeberg wanted to create a device that had a wider range of motion and operated more like a natural limb would. To do so, the FAU team developed a heating process called “Joule” heating. With a 3D printer, they created the inner and outer molds that housed a flexor and extensor actuator and a position sensor. The extensor actuator takes a straight shape when it’s heated, whereas the flexor actuator takes a curved shape when heated, in which currents are passed through a heat-releasing conductor.

In constructing the finger, Engeberg first took a 3D CAD model of a real human digit, then took a 3D printer and created the small, soft (or flesh-like) components of the limb. Within these 3D-printed parts were a flexor actuator and an extensor actuator, with the former taking a curved shape when heated through the Joule process and the latter taking a straightened position.

The result was a heating and cooling based robotic finger that is capable of flexing and extending more quickly than other bionic fingers, and also maintains its natural resting position more completely.

“We have been able to thermomechanically train our robotic finger to mimic the motions of a human finger like flexion and extension,” said Engeberg. “Because of its light weight, dexterity and strength, our robotic design offers tremendous advantages over traditional mechanisms, and could ultimately be adapted for use as a prosthetic device, such as on a prosthetic hand.”

Although preliminary tests certainly suggest that Engeberg’s new finger looks and operates much more naturally than other models on the market, the team is still trying to work out a few kinks, including how long it takes for the heating and cooling process to actually take place. As a result, Engeberg suggests that the first applications of this new technology be in “underwater robotics, because it would naturally provide a rapidly cooling environment.”

So while it may still be awhile until we get to experience this new technology, it just may be the case that the bionic human being is much closer and much more life-like than previously expected.

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