A groundbreaking flapping-wing robot capable of both flying in air and swimming underwater is transforming scientific understanding of how diving birds navigate two vastly different environments. The study, led by Raphael Zufferey and colleagues, highlights new design principles that may revolutionize not only biological research but also the development of versatile aquatic-aerial robots for environmental monitoring.
About 100 bird species uniquely employ their wings to propel themselves efficiently both through air and underwater. Although these birds maintain a broadly similar wing-flapping motion in both media, they adapt by slowing wingbeats and decreasing wing surface area beneath the surface. Given that water is approximately 1,000 times denser than air, the physics of effective locomotion diverge significantly between the two. This disparity demands distinct forces and wing kinematics to optimize propulsion and lift in each. However, investigating these dual-environment dynamics in live birds is challenging, and computational models grapple with capturing the intricate fluid-structure interactions during transitions between water and air.
The robotic platform designed by Zufferey et al. offers a compelling solution by physically embodying the principles governing biological flapping-wing locomotion. The 250-gram untethered robot integrates a sleek fuselage, dual flexible membrane wings, and a movable tail, all in a waterproof chassis equipped with onboard electronics. This configuration allows remote modulation of wing-flapping frequency and tail angles, enabling controlled experimentation on how variations in wing size, flexibility, and motion affect performance in both aerial and aquatic settings as well as during seamless transitions.
Intriguingly, the researchers discovered that complex wing-folding mechanisms—long assumed essential for birds’ dual-function wings—are not critical. Instead, attaining an optimal balance of wing flexibility, size, and beating frequency suffices to achieve comparable propulsion and flight dynamics. Smaller wings, observed in certain diving birds, were found to enhance underwater speed but did not yield greater swimming efficiency, implying that wing reduction may primarily improve maneuverability and prey capture rather than conserve metabolic energy.
Wings possessing intermediate flexibility delivered the greatest overall efficacy. They enabled robust underwater thrust while still generating adequate lift to support flight, embodying a key functional compromise. The team also uncovered that aquatic takeoff powered solely by wing motion, without leg assistance, is feasible albeit energy-intensive. Notably, due to flying requiring significantly less power expenditure compared to swimming, the robot demonstrated greater efficiency in exiting the water to fly over longer distances rather than remaining submerged.
This pioneering robotic model not only sheds light on the evolutionary and physiological adaptations of aerial-aquatic animals but also establishes a versatile platform for future studies in limnology, oceanography, marine ecosystem assessment, and coastal management. By bridging the gap between biological observation and precise physical experimentation, the work unlocks new vistas for understanding—and emulating—the remarkable versatility of nature’s flying swimmers.
Subject of Research: Flapping-wing locomotion in aerial-aquatic environments
Article Title: Leaping out of the water: Aerial-aquatic locomotion with flapping wings
News Publication Date: 9-Jul-2026
Web References: 10.1126/science.aeb6744
Keywords: flapping-wing robot, aerial locomotion, aquatic propulsion, wing flexibility, biomechanical adaptation, diving birds, biomimetic robots, dual-environment locomotion
