Shear Piezoelectricity in Poly(vinylidenefluoride-co-trifluoroethylene): Full Piezotensor Coefficients by Molecular Modeling, Biaxial Transverse Response, and Use in Suspended Energy-Harvesting Nanostructures

An experiment has demonstrated that by analyzing the shear behavior, the response in suspended geometries can be fully rationalized upon taking into account transverse contributions. P(VDF-TrFE) solutions were prepared, and placed into a 1.0 mL syringe tipped with a 27 gauge stainless steel needle. A bias of 25 kV was applied to the needle by a high voltage supply. A grounded cylindrical collector (diameter 8 cm), was placed at a distance of 6 cm from the needle. Properly designed shadow masks were positioned on the surface of the disk to deposit single nanowires. Nanowires with a measured VDF:TrFE ratio of about 70:30] were inspected by SEM with a Nova NanoSEM 450 system (FEI), using an acceleration voltage around 5 kV and an aperture size of 30 μm. Fourier transform infrared spectroscopy was performed with a spectrophotometer using a 4 mm wide beam incident orthogonally to the plane of the samples. The resulting architectures are extremely versatile, and they can find application in devices for nanoscale localization nearby large-scale surfaces and in systems for harvesting vibrational noise, which might activate the piezo-electric response of nanobeams without involving large-scale deformation of the underlying supporting substrates. Coupling flexural deformation and transverse piezoelectric response under compression forces establishes new rules for designing next devices based on polymer piezoelectric nanomaterials.