Review on Polyvinylidene Fluoride-Based Triboelectric Nanogenerators for Applications in Health Monitoring and Energy Harvesting

To meet future demands for sustainable and environmentally friendly technology, many research groups are focusing on triboelectric nanogenerators (TENGs), which can scavenge and convert the available mechanical energy into electrical energy. Researchers are working to comprehend the influence of triboelectric material surfaces as well as the properties that play an important role in determining the overall output performance of TENGs. The selection of tribonegative and tribopositive materials based on the charge in triboseries and different processes for manufacturing the triboactive material and its surface modification play important roles in attaining optimal TENG performance. The most significant tribonegative material is polyvinylidene fluoride (PVDF), and its electroactive polar β-crystalline phase is responsible for higher TENG performance. However, PVDF has some intrinsic limitations such as lower electrical conductivity and dipole moment and nonpolar α-crystalline phase at room temperature. Interestingly, these are the main factors that determine the output performance of TENG applications in energy harvesting and wearable sensors. In this review, we have mainly focused on the influence of varying processing methods like solution casting, 3-D printing, spin coating, and electrospinning on the output performance of PVDF-based TENGs. The effect of nanoscale materials on the PVDF crystalline phase is also studied in detail. Additionally, an extensive analysis of recent advancements in health monitoring, wearable sensors, and energy harvesting applications of PVDF-based TENGs is included.