Derivation of analytical equations with experimental verification for working mechanism of triboelectric nanogenerators in contact-separation mode

Since the invention of triboelectric nanogenerator (TENG) in 2012, various works have attempted to address the basic physical principles of TENG operation such as Maxwell displacement current or air breakdown effect. Nevertheless, physical mechanisms incorporating the measurement system to give a better comprehension of the testing process have not been reported yet. Here, as evidenced by the measurement results of a ZnO-PDMS TENG, we investigate the fundamental mechanisms of short-circuit current and open-circuit voltage output of TENGs in contact-separation mode by analyzing analytical equations based on a capacitor-like and charged-plate model for better comprehension. The analysis can provide deeper insights into the output waveforms of TENGs during contact and separation operations. Moreover, the impact of the testing conditions of a measurement system on the results can be elucidated. The output waveforms could be disguised and misleading to some degree depending on the sampling rate in data collection. More importantly, the inherent resistor associated with the voltmeter dramatically governs the voltage output of TENGs, which is especially sensitive to transfer charge distribution.