The German Aerospace Center (DLR) has popped up here a few times with some very dexterous robots, but apparently they're pretty tough too, like taking a beating from a baseball bat tough. In the video below, the DLR Hand Arm System receives a "stress test," and impressively enough, the arm functions as well afterwards as it did before receiving a blow.

What prevented the arm from being destroyed by the impact are the very same components that allow it to act like a human arm. This is thanks to a mix of 52 actuators and synthetic tendons made from a material called Dyneemathan (it's stronger than Kevlar!), making it hardy as we expect a robot to be.

But rigidity is only half of the equation. The joints and actuators are designed so they can absorb and dissipate energy, too.

Markus Grebenstein, the Hand Arm System's lead designer explained to IEEE Spectrum, "robustness is essential if we want to deploy service robots in the real world, where collisions are likely to happen. Even small shocks can damage conventional robots, which rely on motors coupled to joints in mechanically stiff configurations."

IEEE Spectrum has the full mechanical breakdown if you like to get down with the nitty gritty technicalities of robotic joint designs.