Reviewed by Lexie CornerMar 28 2025
Recent research published in the journal Engineering examines the advancements and challenges in Miniature Underwater Robots (MURs), with a focus on propulsion efficiency in highly resistive aquatic environments. The study reviews conventional and bio-inspired propulsion methods, emphasizing innovations in soft-bodied actuators and AI-driven control strategies aimed at improving maneuverability, energy efficiency, and autonomy.
Applications of MURs from the three aspects: underwater exploration and transportation, narrow space inspection, and autonomous movement. Image Credit: Panbing Wang et al.
Propulsion efficiency is a key focus for Miniature Underwater Robots (MURs), as they operate in a medium with high drag forces, unlike aerial and terrestrial robots.
There are two main propulsion mechanisms: bio-inspired methods that mimic the swimming patterns of marine organisms and conventional methods such as propellers and jet propulsion. Although conventional propulsion systems are well-established, they often face challenges related to energy efficiency and miniaturization.
Bio-inspired propulsion techniques, such as pulsation similar to jellyfish and undulating motion like fish, offer advantages in energy efficiency, maneuverability, and stealth.
Recent developments in soft robotics have improved the adaptability of robots to changing environments, particularly with the development of soft-bodied actuators and shape-adaptive propulsors. The use of flexible materials has made bio-inspired designs more viable as alternatives to conventional propulsion systems.
However, challenges remain. Smaller robots have limited onboard energy storage, making it difficult to reduce actuation systems without sacrificing power output.
Moreover, underwater robots often work in environments where refueling or charging is not practical, making energy efficiency a critical issue. This limitation has driven research into ultra-low-power actuators and energy-harvesting technologies.
Another major challenge is achieving precise control and steady movement in unpredictable underwater currents. Researchers are exploring advanced control techniques, such as distributed swarm intelligence and reinforcement learning-based adaptive control, to overcome these challenges and enable MURs to operate independently in complex environments.
The study identifies several areas for further research in MURs. Combining artificial intelligence with real-time environmental perception is expected to significantly enhance autonomy, allowing robots to navigate intelligently without human intervention. AI-driven motion planning algorithms could help MURs optimize their trajectories while minimizing energy consumption.
Additionally, advancements in biohybrid actuation and soft robotics could allow robots to adjust to changing underwater environments and mimic marine life. These innovations could also advance swarm robotics, where multiple MURs collaborate for group monitoring and exploration.
MURs also have potential applications in biomedical fields, such as targeted drug delivery in aquatic environments, environmental monitoring, and underwater infrastructure inspection. Their maneuverability in tight spaces makes them ideal for deep-sea ecological surveys, ship hull maintenance, and pipeline inspections.
As demand for small, efficient, and intelligent underwater robots grows, further progress in actuation mechanisms and control strategies will continue to drive the field forward.
This study provides a comprehensive analysis of actuation techniques, categorizing and evaluating the various propulsion strategies used in MURs, while highlighting their benefits, drawbacks, and areas for improvement.
It also reviews recent advancements in biohybrid swimming mechanisms and soft-bodied actuators, emphasizing their potential to enhance adaptability and energy efficiency. Key challenges in control, power efficiency, and miniaturization are highlighted, offering valuable insights into potential future research that could transform underwater robotics.
The development of miniature underwater robot technologies opens new opportunities in marine science, industry, and healthcare. Researchers plan to combine soft robotics, AI-driven control, and energy-efficient propulsion systems to create next-generation MURs capable of operating autonomously in challenging underwater environments.
These robots have the potential to significantly impact marine conservation, search and rescue operations, and the maintenance of underwater infrastructure.
Journal Reference:
Wang, P., et al. (2024) Actuation and Locomotion of Miniature Underwater Robots: A Survey. Engineering. doi.org/10.1016/j.eng.2024.10.022.