Out‐of‐Plane Polarization in Bent Graphene‐Like Zinc Oxide and Nanogenerator Applications

Abstract

Highly efficient piezoelectric nanogenerator operation is demonstrated based on dynamic bending of graphene-like ZnO nanosheets. Energy is harvested by an external resistor by virtue of a strong time-varying piezoelectric polarization component perpendicular to the graphene-like ZnO plane. It is shown analytically and verified numerically using molecular dynamics simulations that the 6m2 point group of flat graphene-like ZnO is reduced to monoclinic m symmetry for bent graphene-like ZnO. The latter symmetry allows for a nonzero and large piezoelectric polarization component perpendicular to the plane of the 2D structure. The numerical results confirm that flexoelectric effects are negligible subject to graphene-like ZnO bending operation.

Flexoelectricity-Enhanced Photovoltaic Effect in Self-Polarized Flexible PZT Nanowire Array Devices

“…During the simulation, the crystal structure of tetragonal PZT ( P 4 mm ) was employed. Therefore, the polarization change P 3 can be described using polarization in both piezoelectricity and flexoelectricity, which can be expressed as follows: where P 3 = P z is the polarization change along the z direction; e 35 is the piezoelectric coefficient; S 5 = S z is the strain along the z -direction; μ 313 is the flexoelectric coefficient in longitudinal mode; and f 13 is the strain gradient along the z -direction. Figure d presents the flexoelectricity-induced polarization change P 3 at different curvatures.…”

2D Materials as Effective Cantilever Piezoelectric Nano Energy Harvesters

“…Similar conclusions are obtained for MX 2 . As shown in Figure S4, the results agree well with those in ref .…”

“…A BN nanoribbon was reported by López-Suárez et al as an energy harvester that can reach an output of 8 × 10 –12 W if the nanoribbon is pre-strained, which, however, is harder to control. The output of the graphene-like ZnO nanogenerator that we reported earlier is 2.11 × 10 –11 W . The cantilever nanogenerator structure that we study here is simpler, as only one side is fixed.…”

Electroactive Biomaterials Regulate the Electrophysiological Microenvironment to Promote Bone and Cartilage Tissue Regeneration

“…Using barium titanate (BaTiO 3 ) as a case study, it was observed that this compound exhibits a series of distinct crystal structures, namely cubic, tetragonal, orthorhombic, and rhombohedral phases, at specific temperatures, namely 1,460, 120, 0, and ‐90 °C, respectively. [ 151 ] The tetragonal phase of BaTiO 3 is prevalent at room temperature, with Ti 4+ cations exhibiting displacement from the center of a [TiO 6 ] octahedra. This displacement results in the formation of a net polarization along the [001] edge direction.…”