IoT technology PVDF TiO_2?x nanoparticle advanced driver assistance technology axle bearing carbon nanotube carbon nanotubes energy harvesting energy-harvesting metamaterial femtosecond laser ferroelectric frictional force gapless graphene high deformability high dielectric constant hybrid energy layer-by-layer mechanical energy mechanical fatigue resistance mesoporous composite polymer metal oxidation metamaterial sensor microstructures nanoimprinting nanostructures organic composites oxygen vacancy piezoelectric polymers