Towards breath sensors that are self-powered by design
Bio-sensors implanted in the body are revolutionizing healthcare. How to power these sensors is an open challenge. One promising option is to harvest small amounts of energy from the body …
Tunable stiffness in fish robotics: mechanisms and advantages
When fish-like robots tune their stiffness in realtime, they can be much more efficient. Real fish use the same strategy. In this review article, we summarize the latest work on …
Tunable stiffness enables fast and efficient swimming in fish-like robots
Fish are thought to adjust their tail stiffness to swim efficiently over a wide range of speeds, but how they tune stiffness has been a mystery. We derived a model that combines fluid …
How aspect-ratio affects near-ground swimmers
Animals and bio-inspired robots can swim/fly faster near solid surfaces like the seafloor. In the past, researchers had quantified how strong these effects were for two-dimensional airfoils. We studied how …
How thrust and efficiency change if you swim near the bottom of the pool
We developed a model that estimates how thrust and efficiency change as a pitching hydrofoil gets closer to a planar boundary. Our model predicts that the modified forces are caused …
How dorsal fins make fish faster and more efficient
The dorsal and anal fins of fish interact with the tail fins to produce higher thrust and efficiency. We focused on thin elongated dorsal fins, like those of jackfish. We …
Modeling lateral station-keeping in fish
Fish flap their tails asymmetrically to maneuver around obstacles. In contrast, classic fish tail models assume symmetric motions in a uniform flow. We tested how well these classic models work …
Stable equilibria exist for near-surface swimmers and fliers
Fish and birds experience different forces when they swim/fly near a flat surface (e.g. seabed, solid ground, still lake). We discovered that the vertical forces they feel switch from negative …
How lovebirds maneuver through crosswinds in the dark
Pilots need complex instruments and training to safely fly through gusts when their vision is deprived. In contrast, birds fly reliably over open water and at night, despite being more …
Scaling laws for 3D pitching hydrofoils
Building on our previous work on 2-D pitching airfoils, we explored how forces and torques scale for 3-D pitching airfoils. The terms we added to existing theories were inspired by …
Scaling laws for 2D pitching hydrofoils
Modeling the forces and torques on 2-D pitching airfoils is critical for understanding the locomotion of fish and birds. Traditional linear theories can predict some of the forces, but break …
Ninsinusoidal swimming/flying gaits
Existing studies of fish and bird locomotion typically assume the fins/wings oscillate sinusoidally. We explored what happens when the oscillations range from triangle waves to square waves. Triangle waves behave …
A low turbulence wind tunnel for birds
We worked with the Jacobs Engineering Group to build a wind tunnel specifically designed for studying birds. The test section is about 1 m wide and can reach speeds of …
Limitations of modeling the wake around bird wings
Estimating lift from the flow around flapping wings is critical for studying bird flight. To test existing lift theories, we measured the flow around a parrotlet’s wing as it flew …
Optimizing the efficiency of flexible swimming panels
Simplified geometries can be used to isolate the effects of flexibility in swimming fish. Here we used an oscillating flexible rectangular panel to explore how efficiency is affected by frequency, …
Side-by-side propulsors show high thrust and efficiency when tuned properly
When fish swim in a school, they interact hydrodynamically with one another. We explored these interactions by testing two rigid pitching airfoils side-by-side in a water channel. We found that …
Flexible panels produce more thrust near solid boundaries
We extended our work on rigid airfoils and discovered that flexible panels also produce more thrust near a solid boundary. This time, we checked swimming speed directly and confirmed that …
Pitching airfoils produce more thrust near solid boundaries
Airplanes gliding near the ground experience experience a boost in lift. We discovered that this boost extends to unsteady lift forces, such as those governing thrust production in fish. Fish …
Scaling the efficiency of flexible swimming panels
Simplified geometries can be used to isolate the effects of flexibility in swimming fish. Here we used an oscillating flexible rectangular panel to explore how efficiency scales with panel stiffness …