Fig. 1.

The main modes of triboelectric nanogenerators (TENGs) and examples of construction: a four main working modes, and b example of the surface modification of the polymer-based TENG. Reprinted with permission from Ref. [30]. Copyright (2012) American Chemical Society. c Example of construction of a TENG operating under the contact-separation mode using springs. Adapted with permission from Ref. [36]. Copyright (2013) American Chemical Society. d Schematic illustration of the polymer TENG operating under the contact-separation mode using a spacer. Reprinted with permission from Ref. [39]. Copyright (2012) American Chemical Society