Spray Fluidized\nBed Assisted Flexible Robust Lightweight\nHollow Metallic Sphere Based Triboelectric Nanogenerator

Lightweight hollow metallic spheres are attracting significant\ninterest for nanogenerator applications due to their exceptional combination\nof low density and high mechanical strength. This balance of structural\nintegrity, reduced mass, and high specific strength is essential for\nensuring the durability and long-term performance of nanogenerator\ndevices optimized for efficient mechanical energy harvesting. In this\nwork, we have fabricated lightweight and high-performance Fe–Cr–Ni\nalloy hollow metallic sphere (HMS) based triboelectric nanogenerators\n(TENGs) as robust energy-harvesting devices. The HMS was fabricated\nby using a method involving sacrificial expanded polystyrene (EPS)\nand a metal slurry to enhance the mechanical properties and energy\nconversion efficiency of the TENG device as compared to the uncoated\nEPS based device. Comprehensive characterization of the physical morphology,\nchemical composition, and microstructural properties of both HMS and\nEPS was conducted. The electronic properties of HMS, with a work function\nof 4.23 ± 0.2 eV, were found to be superior to those of EPS,\nwhich exhibited a work function of 4.49 ± 0.2 eV. This difference,\nhighlighted by significant variances in potential observed in surface\nKelvin probe force microscopy (SKPFM) measurements, indicates a higher\nefficiency in electron transfer and charge storage capabilities for\nHMS. Furthermore, the dielectric constant (κ) of HMS was determined\nto be exceptionally high, measuring 1.6 × 10<sup>7</sup> at a\nlow frequency of 10 kHz and reaching 3.7 × 10<sup>7</sup> at\na frequency of 2 MHz. These properties are integral to the high-performance\nTENGs that incorporate HMS and EPS with a flexible ITO-coated PET\nsubstrate, demonstrating remarkable energy-harvesting capabilities.\nNotably, the HMS-based nanogenerator exhibits an energy output of\n25 V even under minimal pressure, significantly outperforming the\nEPS-based nanogenerator. The findings confirm the potential of HMS-based\nTENGs as robust, lightweight solutions for effective mechanical energy\nscavenging, suggesting substantial applicability in current and emerging\nenergy technologies.