TU Delft uses flying squirrel as inspiration for new drone design

Gliding silently through dense forests at night, flying squirrels perform some of the most agile aerial maneuvers found in nature. Unlike birds, which rely primarily on their feathered wings, gliding mammals reshape their entire bodies during flight: stretching their limbs, deforming their soft membranes (patagia), bending their spines, and actively using their tails to control airflow. Now, scientists at Delft University of Technology have translated these biological principles into a new flying robot called the SquirrelDrone, demonstrating for the first time how whole-body morphing can dramatically improve flight performance in robotic systems.

The study, published in Nature Communications, introduces a fundamentally new approach to morphing aircraft inspired not by birds, but by gliding mammals such as flying squirrels and colugos. With this bio-inspired technology design, we could learn from nature to give future drones extraordinary agility, stability, and maneuverability in flight.

Flying squirrel and drone comparison. Squirrel images are AI-generated.

Fly like a squirrel

“For decades, research on bio-inspired drones has focused primarily on avian-inspired flight: morphing wings with adjustable sweep and twist, flapping motion, or feather-inspired structures,” says Salua Hamaza, Associate Professor in Aerial Physical Interaction and Embodied Intelligence at Delft University of Technology. “But gliding mammals achieve flight control differently. They morph their entire body as an integrated aerodynamic system”.

And this is precisely what led to the research questions: what is the role of coordinated full-body morphing in mammals and its implications for the aerodynamics of flying squirrels? To answer this question, the research team developed the SquirrelDrone. 

This new flying robot reproduces three main biological mechanisms found in gliding mammals:

1. Coordinated forelimb and hindlimb motion to reshape the aerodynamic body during flight.
2. Spine and tail morphing to continuously alter wing posture and orientation.
3. A soft passive membrane, similar to the squirrel’s patagium, that naturally deforms under airflow to enhance lift and drag when needed.

Together, these mechanisms create a fully morphing aerial body rather than a traditional aircraft with rigid wings and separate control surfaces.

Testing it out

To evaluate the system, the research team conducted extensive wind tunnel experiments and outdoor flight tests. Liming Zheng, PhD candidate: "Because the drone changes its entire body shape during flight, we could not evaluate it like a conventional fixed-wing aircraft. We developed four prototype versions and combined many rounds of wind-tunnel experiments with indoor and outdoor flight tests. It was a challenging process, but essential for turning a biological concept into a working robotic system."

The results showed that whole-body morphing significantly improved three key flight characteristics, with different body movements contributing to different aerodynamic effects: 

• Agility: enables rapid rotations and fast reorientation during flight.
• Maneuverability: coordinated changes in body configuration support sharper turns and steeper pull-up trajectories.
• Stability: passive membrane deformation and tail/body morphing improve stability while coordinated limb morphing enhances rolling stability as well.

The findings suggest that future aerial robots could become significantly more adaptive, efficient, and robust by incorporating soft morphing structures instead of relying solely on conventional aircraft designs or discrete control surfaces.

The researchers believe this work could open the door to a new generation of morphing aerial vehicles capable of transitioning seamlessly between stable gliding and agile maneuvering in complex environments.