No and no. Electrical generators/motors are already nearly perfect. The difference here it that these ones are really tiny. Oh, and it says nothing about if they can build them any way except manually one at a time.
You have to admit, making them self-replicating would be pretty cool … for a time.
Yeah, self-replicating machines could be cool. Not necessarily dangerous, too, depending on exactly how robust and good at using a variety of materials they are. If we just make a slightly different version of delicate seafloor bacteria that’s not very scary.
That being said, you could 3D print most of a normal electric motor. I’d have to actually read the research to know how this triboelectric design compares.