Triple-electrode integrated self-supporting triboelectric nanogenerators with high output and durability based on dynamic supercritical carbon dioxide foaming

Durable and sustainable energy harvesting in harsh environments using triboelectric nanogenerators (TENGs) is a grand challenge. Herein, highly compacted and integrated TENGs are developed using dynamic supercritical carbon dioxide (scCO2) foaming technique. The self-assembled internal-electrode TENG (SAI-TENG) which is consisted of a polydimethylsiloxane (PDMS) coated internal metal electrode covered by a corrugated wrinkled foam (CWF) is readily obtained by the foaming process. The CWF can support itself and maintains air gaps to facilitate contact electrification and the biomimetic wrinkles that are induced by the scCO2 flow field, greatly enhance the triboelectric output performance. By sandwiching the SAI-TENG using two internal-electrode PDMS films, a triple-electrode integrated self-supporting TENG (TIS-TENG), which has eight-friction layers in a single device, is developed. The TIS-TENG realized maximum utilization of the wrinkled CWF surface, which is equivalent to three parallel connected TENGs. Moreover, the output was further boosted by adding tea powders and patterning micro domes on the PDMS films, which resulted in a high Voc of 106.3 V and a power density of 32.5 mW/m2. Attributing to the embedded electrode and high elasticity of CWF, the TIS-TENG has remarkable stability and tolerance to harsh conditions and can be used as self-powered sensors for monitoring vehicle parking and working conditions of workers. This work provides new insights into the green fabrication and development of highly integrated self-supporting TENGs with high performance and durability.