Harvard's Robot Cockroach Walks, Swims, and Crawls Underwater


One of the buildings of Harvard University. / Photo by: Daderot via Wikimedia Commons


A cockroach can survive underwater, but for only 30 minutes before suffering the consequences. This trait and the size of the insect has been applied in a robotic unit, enabling it to explore underwater environments for a longer period.

The robotic cockroach is called Harvard’s Ambulatory Microrobot or HAMR. It has the capacity to walk normally on land, swim on the surface of water, and step on underwater terrain. The research team used multifunctional footpads, asymmetric flaps, and custom swimming gaits to support its mobility underwater. Additionally, they implemented a modification called electrowetting so it can sink to the bottom of a body of water.

On land, it utilizes its a built-in gait to walk normally. When set to swim mode, the robot switches to its footpads to rely on surface tension to trigger buoyancy, an upward force that keeps it from sinking, while the swimming gaits allow it to swim. In order to submerge underwater, the synthetic cockroach needs to activate electrowetting by applying a voltage to break the surface tension.

Once submerged, the robot can simply use the same gait its uses on land to walk on the underwater terrain. To protect it from short-circuiting, the engineers coated the robot with Parylene, a transparent, thin film coating that repels extreme pressure and temperature conditions. For it to return to dry land, the team stiffened the robot’s transmission and installed soft pad on its front legs. It lets the payload capacity increase and redistribute the friction from rising to the water surface, which is needed to imply the physics when resurfacing.

“This research demonstrates that microrobotics can leverage small-scale physics -- in this case, surface tension -- to perform functions and capabilities that are challenging for larger robots," stated Kevin Chen, the first author of the study at the School of Engineering and Applied Sciences at Harvard University.

The tiny robotic unit weighs 1.65 grams, can carry additional payload of 1.44 grams, and can paddle its legs with a frequency of up 10 Hz. The researchers will conduct further studies to improve the mobility of HAMR.