Triboelectric nanogenerators with porous and hierarchically structured silk fibroin films via water electrospray-etching technology

Abstract

Abstract Triboelectric nanogenerator (TENG) has great potential applications in self-powered electronic devices, especially in flexible and wearable applications. Currently, to improve the performances, micro/nano structured surfaces are constructed in TENGs using complicated, costly, and toxic processes. Herein, a cost-effective and versatile water electrospray-etching (ESE) process for fabrication micro/nano structured silk fibroin (SF) triboelectric film has been presented. The water-soluble SF film could be easily dissolved by the atomized water droplets, meanwhile, as the residual charges on the droplets transferred and accumulated on to the SF surface, a patterned electrical field emerged due to the peak effect on the etched crater-like structures and manipulated the positions of deposition of the charged droplets. Our ESE strategy, which was different from the randomly distributed deposition by conventional electrospray deposition (ESD) process, could obtain quasi-periodical and porous structures, providing significantly increased surface roughness. The structural features, such as period and depth of the micropores, could be controlled by adjusting the spray parameters. The maximum output voltage and power density of the TENGs with porous structures were obviously increased by 180%, compared to 100 V obtained for a planar device. Furthermore, hierarchical micro/nano structures could be simply obtained by mixing SiO2 nanospheres in the aqueous precursor solution as nano-electrets. With this, the output voltage was up to 260 V, representing an overall 260% increase over the value of a planar device. The highest total power and peak power density were 0.65 mW and 161.5 μW/cm2 at a driving force of 18 N and frequency of 1 Hz. Meanwhile, the porous SF based TENG exhibited higher transmittance due to light scattering effects. The proposed water ESE strategy has advantages such as low cost, large area applications, bio-compatibility and nontoxicity, showing great promise as a technology in practical use.