“…A thin-film micro-grating triboelectric generator produced 50 mW/cm 2 with conversion efficiency of 50%; other devices reached 85% energy conversion efficiency, when operated at low frequency [53]. Many other groups developed new types of tribogenerators, often based on the setups developed by Wang's group, contributing to the large number of recent publications [54][55][56][57][58][59][60].…”