A triboelectric generator based on self-poled Nylon-11 nanowires fabricated by gas-flow assisted template wetting

• Published in: Energy & environmental science 2017-10, Vol.1 (1), p.218-2189
• Main Authors: Choi, Yeon Sik, Jing, Qingshen, Datta, Anuja, Boughey, Chess, Kar-Narayan, Sohini
• Format: Article
• Language: English
• ISSN: 1754-5692; 1754-5706
• DOI: 10.1039/c7ee01292f

Triboelectric generators have emerged as potential candidates for mechanical energy harvesting, relying on motion-generated surface charge transfer between materials with different electron affinities. In this regard, synthetic organic materials with strong electron-donating tendencies are far less common than their electron-accepting counterparts. Nylons are notable exceptions, with odd-numbered Nylons such as Nylon-11, exhibiting electric polarisation that could further enhance the surface charge density crucial to triboelectric generator performance. However, the fabrication of Nylon-11 in the required polarised δ′-phase typically requires extremely rapid crystallisation, such as melt-quenching, as well as "poling" via mechanical stretching and/or large electric fields for dipolar alignment. Here, we propose an alternative one-step, near room-temperature fabrication method, namely gas-flow assisted nano-template (GANT) infiltration, by which highly crystalline "self-poled" δ′-phase Nylon-11 nanowires are grown from solution within nanoporous anodised aluminium oxide (AAO) templates. Our gas-flow assisted method allows for controlled crystallisation of the δ′-phase of Nylon-11 through rapid solvent evaporation and an artificially generated extreme temperature gradient within the nanopores of the AAO template, as accurately predicted by finite-element simulations. Furthermore, preferential crystal orientation originating from template-induced nano-confinement effects leads to self-poled δ′-phase Nylon-11 nanowires with higher surface charge distribution than melt-quenched Nylon-11 films, as observed by Kelvin probe force microscopy (KPFM). Correspondingly, a triboelectric nanogenerator (TENG) device based on as-grown templated Nylon-11 nanowires fabricated via GANT infiltration showed a ten-fold increase in output power density as compared to an aluminium-based triboelectric generator, when subjected to identical mechanical excitations. Highly crystalline and "self-poled" δ′-phase Nylon-11 nanowires, fabricated using a novel gas-flow assisted nano-template infiltration method, exhibit enhanced triboelectric energy harvesting performance.