Fabrication and characterization of low-cost flexible triboelectric nanogenerators for efficient and sustainable ambient energy harvesting

This work focuses on the development and characterization of flexible triboelectric nanogenerators (TENGs) using low-cost polymers: high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyurethane (PU), and poly (methyl methacrylate) (PMMA). The materials were synthesized into thin films by a solvent casting method. Scanning Electron Microscopy (SEM) showed different surface morphologies, like ductile and brittle natures. Mechanical testing indicated PMMA has higher tensile strength (35 MPa) and better stiffness properties than TPU, which has better flexibility and elastic properties. Fourier Transform Infrared Spectroscopy (FTIR) confirmed the presence of functional groups (C = O and C-O-C) in PMMA and TPU, which are important for charge transfer. X-ray diffraction showed that HDPE had the highest crystalline content (70%) and a large crystallite size (30.17 Å), which explained its effective tribo-negative material. PMMA and TPU had low crystalline materials (<1%), which enhanced any tribo-positive properties. Differential scanning calorimetry (DSC) suggested that a blend of TPU and PMMA had a melting temperature (Tm) of 175.8 °C and even had better thermal stability than TPU or PMMA polymers. A demonstration of the dielectric study illustrates that PMMA had the largest dielectric constant at high frequencies. A 3D-printed model was fabricated for testing the tribo-model (contact-separation), which produced a peak-to-peak voltage output of 155 V in a TPU/PMMA-HDPE TENG. The results show that intentionally combining the polymers and their various mechanical, thermal, and electrical characteristics was able to achieve a TENG that could be efficient, scalable, and low-cost.