While there is always room for improvement, roboticists have been pretty successful at building robots for dedicated jobs. When a robot only needs to do one task really well, they can usually outperform humans. But, they lack the versatility that humans possess, and the ability to seamlessly switch between jobs. The same is true for mechanical prosthetics, but this new 3D-printed prosthetic hand is one step closer towards recreating human capability.
Building a useful prosthetic hand has many inherent challenges, but one of the biggest is how to provide both speed and strength. The human muscular system is capable of both, and can switch between the two or combine them as needed. But, robots are limited by their motors or actuators. To switch between torque and speed, they generally need some sort of cumbersome transmission system. The new ADEPT (adaptively driven via elastomeric passive transmissions) hand also incorporates a kind of transmission, but it’s far more practical than traditional geared designs.
Like many prosthetic hand designs, ADEPT’s fingers are contracted by winding tendon-like cords on a spool. The size of that spool determines whether the fingers move quickly or with a lot of torque. To switch between the two, ADEPT’s spools are deformable and their diameter can be modified by tightening separate tendons. If the spool diameter is large, the fingers can quickly close. If it’s small, the fingers can grip with a lot of force. Those are the same basic principles behind mechanical advantage, and the concept that makes your car’s transmission useful.
Compared to conventional transmission systems built with precisely machined gears, this has the benefit of being 3D-printable and affordable. It’s estimated that an entire ADEPT hand could be built for less than $500. And, because they’re 3D-printed, designs could be modified on the fly to better suit individual users.