Piezoionics: Mechanical‐to‐ionic transduction for sensing, biointerface, and energy harvesting

Abstract Piezoionic materials consisting of a polymer matrix and mobile ions can produce an electrical output upon an applied pressure inducing an ion concentration gradient. Distinct from charges generated by the piezoelectric or triboelectric effects, the use of generated mobile ions to carry a signal closely resembles many ionic biological processes. Due to this similarity to biology, the piezoionic effect has great potential to enable seamless integration with biological systems, which accelerates the advancement of medical devices and personalized medicine. In this review, a comprehensive description of the piezoionic mechanism, methods, and applications are presented, with the aim to facilitate a dialogue among relevant scientific communities. First, the piezoionic effect is briefly introduced, then the development of mechanistic understanding over time is surveyed. Next, different types of piezoionic materials are reviewed and methods to enhance the piezoionic output via materials properties, electrode interfaces, and device architectures are detailed. Finally, applications, challenges, and outlooks are provided. With its novel properties, piezoionics is expected to play a key role in the overcoming of grand challenges in the areas of sensing, biointerfaces, and energy harvesting.