Cam-based sustainable triboelectric nanogenerators with a resolution-free 3D-printed system

Abstract Abundant rotating energies in our environment could be utilized to produce electrical power by using mechanical energy harvesters; however, rotating scavengers are limited by their low lifetimes and high costs due to the severe friction between operating materials and the necessity of precise system resolution. In this study, we report cam-based triboelectric nanogenerators (C-TENGs), where the cam transforms rotational motion into linear movement, resulting in a practically-sustainable high-performance scavenger that utilizes contact-type TENGs. Furthermore, we use bumper springs in the C-TENG system to create cost-effective and resolution-free C-TENGs, which allow the low-resolution system elements (i.e., 3D-printed components) to be easily rotated without experiencing blocking. It is demonstrated that the ratio between the spring constants of a spacer spring and a bumper spring is an important design variable to improve the output power of the C-TENG. Interestingly, we also find that the rigidity of the supporting substrate below the contacting materials is significant and enhance the output performance of TENGs over twice by adopting soft substrates. By augmenting the number of cam noses, the working frequency increases, but the output peak power is not changed due to the same contact velocity in the C-TENG. Alternatively, the output power in the C-TENG is extremely dependent on the angular velocity where the contact velocity significantly increases. We suggest that the contact velocity could be determined by analyzing the separation time in the C-TENG; this is useful because it is difficult to directly measure the velocity. Our C-TENG is demonstrated to produce a uniform high output voltage (~350 V) for a long time (over 210,000 cycles) at 400 rpm. The maximum output energy and average power of our C-TENG are calculated to be 6.7 µJ and 3.5 mW at 15 MΩ, respectively. The C-TENG is practically used to power 180 commercial green light-emitting diodes (LEDs) with a bicycle. We expect that this sustainable and resolution-free 3D-printed system design will be a practical and promising solution for industrial applications of TENGs.