Dipole moment distribution models of the hexagonal (a) and orthorhombic (b) structures of FF peptide nanotubes . (c and d) Simulation of electric potential in nanowires 500 nm long and 50 nm in diameter. (c) Piezoelectric potential in a - plane slice for FF peptide (left) and ZnO (right) nanowires under 10 nN of compressive force. (d) Piezoelectric potential in a - plane slice for FF peptide (left) and ZnO (right) nanowires under 10 nN transverse force. Insets show regions of potential reversal at the nanowire roots . Growth of vertical FF peptide microrod arrays with polarization controlled by the positive EF (electric field) (e) and the negative EF (f). The large arrows are directions of applied electric fields, and the plus and minus signs indicate the polarizations of the FF molecules and FF microrods . (g) Open-circuit voltage response of a layer of γ-glycine seed crystals, orientated along the crystallographic b axis. Manual force was applied along the crystallographic b axis over time .