An approach to durable PVDF cantilevers with highly conducting PEDOT/PSS (DMSO) electrodes

Bimorph cantilevers were fabricated using the piezoelectric polymer [poly(vinylidenefluoride), PVDF, β phase] for the active layers and the highly conducting polymer [poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate), PEDOT/PSS] treated with a dimethyl sulfoxide (DMSO) solvent for the electrodes. The PVDF films were modified so as to have high adhesion at the interface between the PVDF and the PEDOT/PSS (DMSO) film by using an ion-assisted-reaction (IAR) method. A diffusion barrier was formed on the PEDOT/PSS (DMSO) surface after the IAR treatment. The barrier on the IAR treated electrode prevented the epoxy from penetrating into the PEDOT/PSS (DMSO) film, while the adhesive penetrated into the untreated electrode. In order to confirm the penetration of the epoxy adhesive into the IAR treated PEDOT/PSS (DMSO), X-ray photoelectron spectroscopy (XPS) spectra and scanning electron microscopy (SEM) images were analyzed. The surface resistance of the IAR treated electrodes was measured with a 4-point probe. The tip displacement of the cantilevers was measured at a resonance frequency, and the deformation of the PVDF film with the IAR treated PEDOT/PSS (DMSO) electrodes was found to be higher than that with PEDOT/PSS or inorganic electrodes at the same input voltages. The cantilevers made with indium tin oxide (ITO) or platinum (Pt) electrodes became damaged after operating the devices at a high frequency or a high input power. The PVDF cantilevers made with the PEDOT/PSS (DMSO) electrodes were found to be electrically and mechanically durable when operating at both high input voltage and high frequency.