Here's the X-Finger in action, an amazing artificial finger that can replace a real finger without any kind of electronics. As the video shows, it allows amputees to recover their full grip to do anything they want, from typing on a keyboard to playing golf and—my favorite part, this—using a cocktail shaker. The device's mechanism is quite simple and ingenious.
To start with, it doesn't require any batteries, as it uses the force of the body's own muscles. They are activated "by moving the residual finger when available, or the opposing finger when needed."
Thanks to its artificial tensors and the articulation's design, moving the residual fingers triggers a natural motion on its artificial phalanges, making it look as you are flexing a real finger. This means that the X-Fingers can be controlled independently, giving you a grip that is strong enough to do almost every normal task.
The fingers, which weigh less than 10 grams on their own and about 30 grams when covered with a silicon skin, are custom-made to fit the patient's anatomical characteristics and can be easily put on or removed.
And of course, they will allow some patients to give people the finger, which along with the cocktail shaking, to me is reason enough to rabidly applaud the invention.