This article presents a comprehensive technical survey on the mechanical design of multi-domain multirotors (MDMs) – unmanned aerial systems capable of operating across diverse environments, specifically aerial-terrestrial, aerial-aquatic, and triphibious domains. Owing to their capacity for seamless transition between distinct media, MDMs have garnered significant attention for their potential in critical applications such as disaster response and environmental monitoring. However, existing literature has not sufficiently addressed the inherent design complexities and structural challenges of MDMs, particularly regarding the integration of multi-domain propulsion, actuation, and locomotion mechanisms. To address this gap, this survey systematically classifies MDM designs based on operational modes and actuation systems. It highlights key mechanical innovations, including reconfigurable architectures and multi-propulsion strategies. Finally, the survey identifies current research limitations and outlines pivotal directions for future investigation.
