MWCNT@SiO₂ Heterogeneous Nanofiller-Based Polymer Composites: A Single Key to the High-Performance Piezoelectric Nanogenerator and X-band Microwave Shield

We report the prototype fabrication of a flexible, facile multiwalled carbon nanotube@ silica incorporated poly(vinylidene fluoride) (MWCNT@SiO2/PVDF) nanocomposite-based piezoelectric energy harvester as a cheaper and cleaner source of alternative energy. In depth study of local piezoelectric and ferroelectric properties of the nanocomposites was performed by the piezoresponse force microscopy (PFM) technique. The prototype piezoelectric nanogenerator scavenges low-frequency biomechanical energy and the abundant vibration energy of the ambient environment to produce remarkable electrical power (it can directly illuminate a panel of 55 commercial LEDs), without applying any external poling process. The flexible nanogenerator exhibits high performance with a maximum recordable output voltage of 45 V, current density of 1.2 μA/cm2, and power density of 5400 W/m3 under periodically vertical compression and release operations via biomechanical force. The high efficiency (15.4%) of the nanogenerator led to a unit cost of electricity as low as 0.21 US$/kWh, which is extremely competitive to other energy sources. Again, the self-standing MWCNT@SiO2/PVDF nanocomposite film shows an extremely effective electromagnetic interference (EMI)-shielding property in the X-band, with the promise to block the detrimental effect of microwave radiation on the environment. The flexible films with a thickness of 400 ± 5 μm were found to exhibit about 99% microwave shielding in the X-band (8.2–12.4 GHz) with a dominating fraction of absorption. These results undoubtedly expand the feasibility of such heterogeneous nanocomposites in energy and environmental sectors for high-performance energy-harvesting devices as well as microwave-shielding applications like wearable devices for power production from human body movements that simultaneously protect the human body from microwave radiation.