By imitating the behavioral characteristics of some typical animals, researchers develop bionic stepping motors to extend the working range of piezoelectric materials and utilize their high accuracy advantage as well. A comprehensive review of the bionic stepping motors driven by piezoelectric materials is presented in this work. The main parts of stepping piezoelectric motors, including the feeding module, clamping module, and other critical components, are introduced elaborately. We classify the bionic stepping piezoelectric motors into inchworm motors, seal motors, and inertia motors depending on their main structure modules, and present the mutual transformation relationships among the three types. In terms of the relative position relationships among the main structure modules, each of the inchworm motors, seal motors, and inertia motors can further be divided into walker type, pusher type, and hybrid type. The configurations and working principles of all bionic stepping piezoelectric motors are reported, followed by a discussion of the advantages and disadvantages of the performance for each type. This work provides theoretical support and thoughtful insights for the understanding, analysis, design, and application of the bionic stepping piezoelectric motors.

Birds have developed near-perfect structures and functionality over millions of years of natural evolution. To improve the efficiency of fixed-wing vehicles in different environments, researchers have developed deformable wings inspired by the wing structures of birds. Shape Memory Alloy (SMA) is applied as a smart material to the deformable wing. Compared with other drive methods, SMA actuators have the advantages of high drive capacity and a simple structure for driving wing deformation. According to the shape memory effect, SMA actuators are classified as single-range and dual-range actuators. The wing structure designed for each SMA drive is unique. By comparing and analyzing the structures of airfoils, airfoils with similar drive forms and deformation structures are put together for review and discussion. The deformable wings are categorized into out-of-face deformation, in-face deformation, airfoil curvature deformation, and combined deformation with multiple degrees of freedom based on the structure and location of the wing that produces the deformation. An overview of the deformed wing is introduced by telling the bionic theory of seagulls. The principles of deformation of the wing, the mechanics of the SMA actuator mechanism, and the aerodynamic characteristics of the deformable wing are presented. The structure and working principle of SMA actuators for each type of deformable wing are explained in detail. Methods and approaches to study the deformability of deformable wings are analyzed and summarized. This work provides comprehensive insights and perspectives for future studies of SMA-driven deformable airfoils.