Hierarchical Micro-Nano Patterned Modified PDMS Triboelectric Nanogenerator Enhanced by Carbon-Based Nanofillers

Triboelectric nanogenerators (TENGs) have received recent interest in converting unconventional mechanical energy to electricity, particularly as a sustainable form of energy generation from sources such as wind and friction. Energy conversion in TENGs is based on the triboelectrification and electrostatic induction effects. In this regard, Polydimethylsiloxane (PDMS) elastomer has been widely used as an excellent triboelectric active layer in TENG owing to its high electronegativity as ranked in the triboelectric series of different materials. The TENGs based on PDMS exhibit a relatively high energy conversion efficiency. However, its output electrical characteristics still need more development. Increasing the triboelectric polymer dielectric constant enhances the current density significantly by facilitating the charge transfer from the contact surface toward electrodes. Nanoparticles' presence enhances charge transfer in TENGs due to increasing the polymer matrix's dielectric constant when their concentration meets the percolation threshold. However, the TENGs' performance has not been investigated from the window of dielectric properties of polymer triboelectric active materials. The shape and sometimes the angle of nanoparticles also play a role in the outcome of the polymer's dielectric constant. This research investigates the effect of carbon-based nanoparticles on PDMS nanocomposite/aluminum TENG output, considering the aforementioned factors. The particles are chosen from various molecular shapes and dielectric constants, including carbon black (CB), carbon nanotube (CNT), graphene oxide (GO), and reduced graphene oxide (r-GO). On the other hand, one of the most practical approaches to enhancing the output performance of TENG is modifying the contact area between triboelectric active material layers. Patterning the surface and changing the shape and density of patterns on the surface is assumed to be an effective strategy for this purpose. The uniform and periodic nanoscale morphology of optical discs (CD and DVD) were replicated onto PDMS films. By changing the ratio of carbon black, the resolution of the CB/PDMS composite layer increases at 4 wt% and then decreases, which was explained according to the percolation theory of the conductive particles in the polymer matrix. The voltage and current output follow the same trend as the dielectric constant. The GO nanoparticle also shows the same behavior at the 1.5 wt%, which is the percolation threshold of GO in PDMS. However, the reduced graphene oxide aggregates faster because of not having the oxygen-containing chemical group and earlier percolation threshold. The procedure is followed by a sequential development of hierarchical low amplitude patterns made by etching treatment leading to perpendicular wrinkling from the DVD wrinkle lines. This method creates a hierarchical pattern as a superposition on the optical disc pattern. Our hierarchical topographic designed TENG led to a considerably higher current and voltage output. Due to having an efficient shape with higher roughness compared to the original CD and DVD patterns base and the flat PDMS surface. Here is a mathematical correction offered in the dielectric constant equations based on the PDMS nanocomposite dielectric properties investigation. The PDMS nanocomposite/Al TENG corresponding output for each filler is studied and compared with the dielectric properties of the nanocomposite. The mathematical correction is also reflected in TENG voltage and current equations.