Large electrostrictive strain at gigahertz frequencies in a polymer nanoactuator: Computational device design

Using molecular dynamics with a first-principles-based force field (denoted MSXX), we show that large electrostrictive strains (~5%) at extremely high frequencies (over ~ 109 Hz) can be achieved in a poly(vinylidene-fluoride) nanoactuator if the packing density of the polymer chains is chosen appropriately. We control the packing density by assembling the polymer chains on a silicon 〈111〉 surface with one-half coverage. Under these conditions, the equilibrium, zero electric field conformation of the polymer contains a combination of gauche and trans bonds. This structure can be transformed to an all- T conformation by applying an external electric field. Such molecular transformation is accompanied by a large deformation in the direction of the polymer chains. The device shows typical electrostrictive behavior with strain proportional to the square of the polarization.