Prestrain-free electrostrictive film sandwiched by asymmetric electrodes for out-of-plane actuation

This study presents a novel and facile strategy to construct prestrain-free dielectric elastomer (DE) film with large out-of-plane actuation. An extremely soft elastomer of amino functionalized poly(dimethylsiloxane) (NH₂-PDMS) with thickness of ∼446 µm was employed as dielectric matrix, which was sandwiched between two asymmetric PDMS electrodes with distinctly designed mechanical properties. Electromechanical coupling factor (ECF, dielectric constant/elastic modulus) of the DE film increased with amino density coupled into dielectric matrix, providing a strategy to construct a DE actuator (DEA) with large displacement under low electric field. The thin, soft electrode was made of an off-ratio polymer of PDMS doped by conductive graphite microflakes, while the thick, stiff electrode was made of completely cured PDMS elastomer doped by conductive graphite microflakes and Ag nanoparticles. The film thicknesses, Young's moduli, and surface resistances were 54.1 µm, 9.21 MPa, 1.02 kΩ/cm² for the soft electrode, and 166.7 µm, 87.5 MPa, 0.13 kΩ/cm² for the stiff electrode, respectively. The prepared DEA diaphragm exhibited well controlled electromechanical properties by driving voltage or frequency, and a high flection angle of 26.3° at an extremely low electrical field of 8.8 V/μm. Thus, it can be used as intelligent valve flap/pump for microfluidic device and artificial muscle with minimized energy assumption activated by low voltage.