Microporous polyvinylidene fluoride film with dense surface enables efficient piezoelectric conversion

We demonstrate that asymmetric porous polyvinylidene fluoride (PVDF) film, with pores mostly distributed in the bulk but not at the surfaces, can be used as a highly efficient piezoelectric energy generation device. For such microporous PVDF film with dense or pore-free surface, piezoelectric theory shows the efficiency of energy conversion by piezoelectric device depends upon the structure compressibility. Film mechanical properties can be controlled by dispersing micro-scale pores in a polymer matrix with a dense top layer. Piezoelectric output is enhanced by optimization of PVDF micro-structure and electromechanical coupling efficiency. The power output increased three folds with a designed three-dimensional asymmetric porous structure as compared to solid film.