Design Challenges to Expand the Functionality of Drones: Deformable Rotorcraft and Nature-Inspired Flapping Drones

As drone technology rapidly evolves, innovative designs that can change their shape or mimic natural flight mechanisms have emerged. This study systematically categorizes and analyzes these advanced strategies for drone design through a comprehensive review of literature from 2001 to 2025. Two main approaches are examined: deformable drones and nature-inspired drones. Deformable drones are subcategorized into extendable, foldable, and tilting types based on their operational mechanisms. Extendable drones include sliding and scissor-like mechanisms, while foldable drones are classified by folding direction and mechanism, with size variation ratios of 0.37–1.46. Tilting drones are categorized into body, rotor, and arm tilting based on degrees of freedom and weight classifications. Nature-inspired flapping drones are analyzed by mass, wingspan, and flight duration across different actuator types. The findings reveal that deformable drones excel in maneuverability and confined space adaptability, while nature-inspired designs offer advantages in miniaturization and energy efficiency. This study provides the first comprehensive overview of deformable drone technology, offering guidance for specialized applications in environmental monitoring, rescue operations, and urban mobility.