Omnidirectional Energy Harvesting Fleeces

CL Park and B Goh and SH Kim and J Choi, ACS APPLIED MATERIALS & INTERFACES, 15, 36688-36697 (2023).

DOI: 10.1021/acsami.3c06644

Underwater mechanical energy harvesters are of risinginterestdue to their potential for various applications, such as self-poweredocean energy harvesters, monitoring devices, and wave sensors. Pressure- responsivefilms and stretch-responsive fibers, which provide high electricalpower in electrolytes and have simple structures that do not requirepacking systems, are promising as harvesters in the ocean environment.One drawback of underwater mechanical energy harvesters is that theyare highly dependent on the direction of receiving external forces,which is unfavorable in environments where the direction of the suppliedforce is constantly changing. Here, we report spherical fleece, consistingof wool fibers and single-walled carbon nanotubes (SWCNTs), whichexhibit repetitive electrical currents in all directions. No matterwhich direction the fleece is deformed, it changes the surface areaavailable for ions to access SWCNTs electrochemically, causing a piezoionicphenomenon. The current per input mechanical stress of the fabricatedSWCNT/wool energy harvester is up to 33.476 mA/MPa, which is the highestamong underwater mechanical energy harvesters reported to date. Inparticular, it is suitable for low-frequency (<1 Hz) environments,making it ideal for utilizing natural forces such as wind and wavesas harvesting sources. The operating mechanism in the nanoscale regionof the proposed fleece harvester has been theoretically elucidatedthrough all-atom molecular dynamics simulations.

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