Output voltage modulation in triboelectric nanogenerator by printed ion gel capacitors

The triboelectric nanogenerator (TENG) has been investigated intensively during the last decade in terms of power improvement and application as sensors, however, its voltage is usually too high and spike-like to be used directly as a power source for electronic devices. Although there was an effort to adjust the voltage through the circuit design, the complexity and the bulkiness of the circuit board make it difficult. Here, we propose a simple approach to change the spike-like voltage profiles to square-like profiles and adjust the output voltage to be suitable range for electronics. We used printed ion gel electrolyte patterns as capacitors and investigated the effects of dimension of the capacitor, connection types (serial, parallel) of multiple capacitors, and electrochemical conditions. The voltage profile of the TENG-ion gel system was modulated by the contact frequency applied to the TENG, the contact area of the ion gel with the electrode, the type of ions in the electrolyte, reduction/oxidation reaction in the gel, and the connection type (parallel, series) between ion gel patterns. We successfully demonstrated the light emission of a large number of printed electrochemiluminescence patterns.