Piezoelectric materials, with their unique ability for mechanical‐electrical energy conversion, have been widely applied in important fields such as sensing, energy harvesting, wastewater treatment, and catalysis. In recent years, advances in material synthesis and engineering have provided new opportunities for the development of bio‐piezoelectric materials with excellent biocompatibility and piezoelectric performance. Bio‐piezoelectric materials have attracted interdisciplinary research interest due to recent insights on the impact of piezoelectricity on biological systems and their versatile biomedical applications. This review therefore introduces the development of bio‐piezoelectric platforms from a broad perspective and highlights their design and engineering strategies. State‐of‐the‐art biomedical applications in both biosensing and disease treatment will be systematically outlined. The relationships between the properties, structure, and biomedical performance of the bio‐piezoelectric materials are examined to provide a deep understanding of the working mechanisms in a physiological environment. Finally, the development trends and challenges are discussed, with the aim to provide new insights for the design and construction of future bio‐piezoelectric materials.

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Energy harvesting is a topic of intense interest that aims to convert ambient forms of energy such as mechanical motion, light and heat, which are otherwise wasted, into useful energy. In many cases the energy harvester or nanogenerator converts motion, heat or light into electrical energy, which is subsequently rectified and stored within capacitors for applications such as wireless and self-powered sensors or low-power electronics. This review covers the new and emerging area that aims to directly couple energy harvesting materials and devices with electro-chemical systems. The harvesting approaches to be covered include pyroelectric, piezoelectric, triboelectric, flexoelectric, thermoelectric and photovoltaic effects. These are used to influence a variety of electro-chemical systems such as applications related to water splitting, catalysis, corrosion protection, degradation of pollutants, disinfection of bacteria and material synthesis. Comparisons are made between the range harvesting approaches and the modes of operation are described. Future directions for the development of electro-chemical harvesting systems are highlighted and the potential for new applications and hybrid approaches are discussed.

This paper combines experimental and modelling studies to provide a detailed examination of the influence of porosity volume fraction and morphology on the polarisation-electric field response of ferroelectric materials.The broadening of the electric field distribution and a decrease in the electric field experienced by the ferroelectric ceramic medium due to the presence of low-permittivity pores is examined and its implications on the shape of the hysteresis loop, remnant polarisation and coercive field is discussed. The variation of coercive field with porosity level is seen to be complex and is attributed to two competing mechanisms where at high porosity levels the influence of the broadening of the electric field distribution dominates, while at low porosity levels an increase in the compliance of the matrix is more important. This new approach to understanding these materials enables the seemingly conflicting observations in the existing literature to be clarified and provides an effective approach to interpret the influence of pore fraction and morphology on the polarisation behaviour of ferroelectrics. A new general rule to describe the relationship between the polarisation and porosity is also proposed. Such information provides new insights in the interpretation of the physical properties of porous ferroelectric materials to inform future effort in the design of ferroelectric materials for piezoelectric sensor, actuator, energy harvesting, and transducer applications.

Recently, the coupling of ferroelectrics with electrochemical reactions has attracted increasing interest for harvesting waste heat. The change of polarization of a ferroelectric with temperature can be used to influence chemical reactions, especially when the material is cycled near its Curie temperature. In this perspective, we introduce the principle of pyroelectric controlled electrochemical processes by harvesting waste heat energy and explore their potential electrochemical applications, such as water treatment, air purification, and hydrogen generation. As an emerging approach for driving electrochemical reactions, the presence of thermal fluctuations and/or transient waste heat in the environment has the potential to be the primary thermal input for driving the change in polarization of a pyroelectric to release charge for such reactions. There are a number of avenues to explore, and we summarize strategies for forming multi-functional or hybrid materials and future directions such as selecting pyroelectrics with low Curie temperature (<100 C), improved heat conductivity, enhanced surface area or porosity, tailored microstructures, and systems capable of operating over a broader temperature range.