Why triboelectricity is better than piezoelectricity? Why did not they use piezo instead? Does anybody know?

Probably to hit the novelty requirement of publishing. Exploring every avenue and balancing the literature across all possible harvesting methods.

- not a scientist

>The oscillatory pressurization of a water droplet between two electrodes generates electrical energy from the electrification of water by the static charge on the surfaces of the dielectric layers.

simplicity/scale/long lasting?

Also that dielectric-layers to me sounds similar to capacitors and that "closer they are "infinite charge"" not really infinite but with reference to the surface area and distance between the plates... man that was like 4 years ago E&M

It is a good question! It would be nice to see the pros and cons of those both compared. Anybody?