Piezoelectric Polymeric Foams as Flexible Energy Harvesters: A Review

Piezoelectric energy harvesters (PEHs) have the potential to power low‐power electronic devices and can advance, self‐powered, autonomous electronics to the next level. Conventional ceramic‐based piezoelectrics have various properties such as fragility, rigidity, toxicity, high density, and lack of design flexibility which limit their use in more flexible environments. A ton of research has been carried out and published on novel piezomaterials, their transduction mechanisms, analytical models, and electrical circuits to improve various aspects of PEHs. Among these materials, studies on polymeric cellular (or foamed) ferroelectrets or piezoelectrets as PEHs have grown significantly since their discovery. Also, very limited or short reviews are available covering only few aspects. There is a necessity of recognizing their past and present advances in their various generation technology and polymer systems. Herein, a broader review of almost all conventional and recent polymeric foam‐based piezoelectrics for PEH applications is summarized. These cellular polymer piezoelectric systems either in bulk, composite, layered, or film form can be fabricated, and depending on the application and conditions, different polymers groups, mainly, polyolefins, polyester, fluoropolymer, and others, are considered. Their applications and future perspectives are also presented and discussed.