Using a synchronous switch to enhance output performance of triboelectric nanogenerators

Contact-mode triboelectric nanogenerators are high impedance charge sources of high output voltage, but very low current. Recent advances in mechanical energy harvesting have demonstrated contact-mode triboelectric nanogenerators as the most auspicious candidates for energy harvesting purposes. Unfortunately, the integration of contact-mode triboelectric nanogenerators with electronic systems for practical applications poses an intrinsic challenge. At present, harvesting mechanical energy from irregular, low-frequency and low-force motions is a challenge. The output voltage of a contact-mode triboelectric nanogenerator is directly proportional to contact force. A plethora of literature exists on the various switching approaches that indicate the importance of managing the output performance of contact-mode triboelectric nanogenerators. Unfortunately, no work exists regarding switch based contact-mode triboelectric nanogenerators that can offer a revolutionary alternative approach that can be incorporated for mechanical energy harvesting.

University of Pittsburgh researchers led by Professor Mingui Sun developed a switch based contact-mode triboelectric nanogenerator, wherein a switch was to be placed between a contact-mode triboelectric nanogenerator electrode and an external circuit. The team demonstrated that by electrically isolating the contact-mode triboelectric nanogenerator from the external circuit when the switch was open, charge leakage could be prevented and the output performance of the contact-mode triboelectric nanogenerator would in turn be enhanced. Their work is currently published in the research journal, Nano Energy.

The research team initiated their studies by placing a switch between one electrode and the external circuit so as to electrically isolate the contact-mode triboelectric nanogenerator from the external circuit when open, and vice-versa, when closed – for the switch based – contact-mode triboelectric nanogenerator. The team then set up a demonstration to present the versatility of their approach where the switching effect in three contact-mode triboelectric nanogenerators fabricated using different types of dielectric films, namely: bare polydimethylsiloxane, micro-dome patterned polydimethylsiloxane, and polydimethylsiloxane-carbon nanofiber composite, were presented. Eventually, a contact-mode triboelectric nanogenerator integrated with a mechanical prototype switch was successfully fabricated and tested.

The authors observed that under the synchronous switching condition the output performance of the contact-mode triboelectric nanogenerator was considerably enhanced due to the prevention of charge leakage via the external circuit. Additionally, from the comparison with a typical contact-mode triboelectric nanogenerator, the researchers noted that the optimal load resistance was decreased drastically which facilitates electronic circuit design.

The study by Paresh Vasandani and colleagues has demonstrated a novel approach for mechanical energy harvesting wherein a switch is incorporated in a contact-mode triboelectric nanogenerator. Furthermore, the practical viability of the approach has been demonstrated by charging a commercial capacitor and using the stored charge to light up three light emitting diodes. It has been seen that synchronous switching can prevent a charge leakage of up to approximately 60%. To this end, this novel approach offers tremendous potential for development of new designs and applications of contact-mode triboelectric nanogenerators across all its operating modes.