A biologically inspired, flapping-wing, hybrid aerial-aquatic microrobot

Abstract

From millimeter-scale insects to meter-scale vertebrates, several animal species exhibit multimodal locomotive capabilities in aerial and aquatic environments. To develop robots capable of hybrid aerial and aquatic locomotion, we require versatile propulsive strategies that reconcile the different physical constraints of airborne and aquatic environments. Furthermore, transitioning between aerial and aquatic environments poses substantial challenges at the scale of microrobots, where interfacial surface tension can be substantial relative to the weight and forces produced by the animal/robot. We report the design and operation of an insect-scale robot capable of flying, swimming, and transitioning between air and water. This 175-milligram robot uses a multimodal flapping strategy to efficiently locomote in both fluids. Once the robot swims to the water surface, lightweight electrolytic plates produce oxyhydrogen from the surrounding water that is collected by a buoyancy chamber. Increased buoyancy force from this electrochemical reaction gradually pushes the wings out of the water while the robot maintains upright stability by exploiting surface tension. A sparker ignites the oxyhydrogen, and the robot impulsively takes off from the water surface. This work analyzes the dynamics of flapping locomotion in an aquatic environment, identifies the challenges and benefits of surface tension effects on microrobots, and further develops a suite of new mesoscale devices that culminate in a hybrid, aerial-aquatic microrobot.

Design and Take-Off Flight of a Samara-Inspired Revolving-Wing Robot

“…With an ability to hover and the exceptional maneuverability, rotary-wing vehicles, in particular, prove to be a highly versatile platform. At small scales, however, flying robots suffer from limited flight endurance due to the increased dominance of viscous forces [1]. Compared to the fixed-wing counterparts, rotorcraft are less efficient.…”

“…Bird-like morphing wings manifest high performance aerodynamic surfaces [2]. Taking after insects and hummingbirds, millimeter-scale flying robots leverage unsteady force production and leadingedge vortices as a lift enhancement mechanism through the flapping-wing motion [1], [3]. In this work, we take an inspiration from winged achenes or autorotating seeds and propose a revolving-wing robot that is capable of hovering with a promising aerodynamic performance.…”

Light‐Driven Shape Morphing, Assembly, and Motion of Nanocomposite Gel Surfers

“…Directing the motion of micro‐ and nanoscale objects at an air/water interface is important from numerous perspectives, ranging from improving fundamental understanding of biological systems to designing synthetic microrobots and swimmers . Capillary and Marangoni forces can drive motion of sub‐mm‐scale objects, since these forces greatly exceed gravity or thermal energy on this scale .…”

Jumping dynamics of aquatic animals

“…The above provides design considerations for robotics and vehicles transitioning between the air-water interface. There has been recent developments in systems that can perform both water-entry and -exit tasks, such as the AquaMAV [37,38] and the RoboBee [39]. However, both rely on using jet propulsion mechanisms to propel the body out of water.…”