Triboelectric nanogenerator by integrating a cam and a movable frame for ambient mechanical energy harvesting

Transform rotary motion triggered by environmental mechanical energy (e.g., wind) to electrical energy is widely used for energy harvesting. Triboelectric nanogenerators that are used to harvest rotational mechanical energy are mostly based on in-plane sliding or free-standing mode. However, the relative friction between the two contacting triboelectric layers may cause severe abrasion, which reduces the durability of the device and increases the maintenance cost. In this study, we report a combination of a cam and a movable frame for a novel triboelectric nanogenerator (CMF-TENG), which is expected to reduce the abrasion problem and improve the output performance. The cam is designed to transform the rotational motion triggered by ambient mechanical energy to linear movement of the movable frame, leading to a contact-separation of the triboelectric layers within each sub-triboelectrification unit of CMF-TENG, thus electric output can be generated. The average electric output from one subunit of the CMF-TENG achieved around 200 V of open-circuit voltage, 2.9 μA of short-circuit current, and 96 nC of transferred charge at the triggered rotational speed of 60 rpm. The power output increase from 180 μW (1 subunit) to around 728 μW when three subunits were connected in parallel. The output voltage of the CMF-TENG remained almost consistent throughout the roughly 8 h continuously operation, suggesting outstanding robustness and durability of the CMF-TENG. The CMF-TENG harvest energy from wind can light up 113 blue LEDs connected in series at a wind speed of 13.9 m/s with the assistance of a rectifying circuit; and can power a thermometer at the same wind speed condition with the assistance of a rectifying circuit and a capacitor. The results imply that the CMF-TENG can not only be used to harvest energy from the ambient environment, but also can achieve self-powered sensing. Technically, by using this novel design, additional sub-triboelectrification units can be added to improve the electric output of the entire device and the rotational mechanical energy can be harvested more effectively with less abrasion.