Are there any helicopter blades that fold in the middle?
Bending a helicopter blade in the middle is of course possible, but poses many serious problems and risks. The designers would look for different solutions first, like they did for the UH-60.

The blade loads are lift, centrifugal force, and twist. Manufacture the blade with modern composite technology, mount it with the fully articulated hinges that are usually a requirement anyway, and trust the blades with your life because a breakage would be catastrophic.

Any repeated action poses additional risk. Mounting a hinge and lock that operates every time, is not open to human error, and never fails - that is would be the quest for the folding blade designer. 

Of course a folding blade can be designed, like the folding wings on navy fighter aircraft. But not for some arbitrary reason. Only for a vital reason that cannot be solved in any other way.