Shape engineering and manufacturing of piezoceramics for energy conversion—a review

Abstract Piezoelectric ceramics are widely used for energy conversion in devices like transducers and energy harvesters because they can convert mechanical energy to electrical energy and vice versa. The recent development of additive manufacturing (AM) (3D printing) techniques, along with advances in modelling and optimisation methods, has led to the creation of geometrically complex piezoceramics. This article provides a comprehensive overview of the importance of piezoelectric element shapes in the energy conversion process. It covers the main devices discussed in the literature, focusing on the geometry of piezoelectric ceramics. The reviewed works include traditional designs such as multilayers, benders, composites, and mechanical amplifiers, as well as non-traditional shapes like tubes, spirals, helices, shells, topologically optimised piezo elements, and metamaterials. We discuss the general effects of shape on piezoelectric ceramics, modelling approaches for piezoelectric ceramics at the macroscale, and typical optimisation techniques used in design. The most common energy conversion figures of merit for material and device designs are examined, considering application-specific requirements for energy harvesters, ultrasound transducers, hydrophones, robotics, and other common applications. The limitations of traditional processing techniques and the potential of new AM methods are also discussed. This article offers a broad understanding of past piezoelectric device and material designs, providing engineers with a foundation for 3D printing innovative new shapes. Ultimately, we offer perspectives on the control and development of piezoceramic shapes.