Harvard’s Cockroach-Inspired Robot HAMR Upgraded to Swim and Walk Underwater

HAMR – Harvard’s tiny cockroach robot will now be able to swim and walk underwater, in addition to all that it is already capable of doing on land

Harvard’s Cockroach-Inspired Robot HAMR Upgraded to Swim and Walk Underwater

Researchers at Harvard’s John A. Paulson School of Engineering and Applied Sciences have upgraded the Harvard Ambulatory Microrobot, better known by its acronym HAMR, with the ability to transition from land to water, and vice versa, with relative ease.

Even before the upgrade, the centimetre-scale HAMR – developed by a team of researchers at the Harvard Microrobotics Laboratory, under the leadership of Charles River Professor of Engineering and Applied Sciences Robert J. Wood – was a versatile enough land robot, capable of running at high speeds, jumping, turning sharply, climbing, carrying payloads and even falling from great heights, without sustaining damage.

The minuscule HAMR owes is fleet-footedness and its aura of indestructibility to one of nature’s most accomplished creatures, the common cockroach – the biological inspiration behind its conception.

It packs almost all of the capabilities of this hard-to-kill versatile invertebrate.

Each leg of the HAMR is equipped with two actuators that mimic the joints of insects to give it super maneuverability around obstacles.

HAMR can run at speeds of up to ten and a half body-lengths per second and can also climb steep inclines, much like its living counterpart.

Not only that, it can even withstand a decent drop, with no resulting damage, whatsoever.

Also, as tiny as it is, it is capable of carrying payloads twice its own body weight; a feature with great potential for a number of practical and useful applications in coming times, like carrying equipment and sensors through heaps of rubble on search and rescue missions, for example.

“The HAMR platform evolved from our exploration of millimeter-scale fabrication and actuation strategies,” Wood had said about the previous-gen HAMR.

“Our techniques allow us to create robots that don’t sacrifice complexity as the size is reduced and enabled us to create robots that rival some of the capabilities of their biological counterparts,” he said, adding that the robots were “as valuable for biological studies as they will eventually be for tasks such as search and rescue and infrastructure inspection.”

And, now, this next-gen HAMR can also swim on the water’s surface and sink and walk underwater, with the same robotic nimbleness and grace as it has been showing off on terra firma.

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HAMR’s ability to stay afloat and swim on the water’s surface is made possible by partially submerged “multifunctional foot pads that rely on surface tension and surface tension induced buoyancy,” explains Leah Burrows in her July 2nd piece on the subject. She is a Science and Technology Communications Officer at Harvard Paulson School.

“Moving on the surface of water allows a microrobot to evade submerged obstacles and reduces drag,” wrote Burrows.

“Using four pairs of asymmetric flaps and custom designed swimming gaits, HAMR robo-paddles on the water surface to swim,” she elaborated.

“Exploiting the unsteady interaction between the robot’s passive flaps and the surrounding water, the robot generates swimming gaits similar to that of a diving beetle. This allows the robot to effectively swim forward and turn,” she added.

When it’s time for HAMR to submerge, it uses a process called electrowetting to break the water surface tension and sink to the bottom and settle on its four feet, before it can begin its underwater walk, moving as smoothly as it does on dry surfaces.

Electrowetting, by the way, is the process of applying a voltage to reduce the angle of contact between an object and the water surface, thereby minimizing surface resistance, which makes it easier for the object to sink.

According to SEAS undergraduate and co-author of the research paper Neel Doshi, the new HAMR owes its swimming and sinking capabilities to its size – too big, and it would be difficult to keep it afloat; too small, and the robot would not be able to produce enough power to break the water surface.

“HAMR’s size is key to its performance,” says Doshi. “If it were much bigger, it would be challenging to support the robot with surface tension and if it were much smaller, the robot might not be able to generate enough force to break it.”

One of the biggest challenges facing this version of HAMR was overcoming the surface tension in order to emerge from the water and transition to dry surface.

The brilliant minds at the Harvard Microrobotics Laboratory found the solution in a more rigid transmission and soft pads on the HAMR’s front paws for redistributing friction, making it possible for the roach-robot to climb out of the water on to dry land with the help of a gently-inclined ramp.

“This robot nicely illustrates some of the challenges and opportunities with small-scale robots,” says Wood.

“Shrinking brings opportunities for increased mobility – such as walking on the surface of water – but also challenges since the forces that we take for granted at larger scales can start to dominate at the size of an insect.”

Well aware of HAMR’s potential for application in a myriad of scenarios, both on land and underwater, its developers are motivated enough to make it more application-friendly, by working on areas of improvement like removing the need for a submerged incline to walk out of the water.

According to Engadget’s Jon Fingas, the team is already weighing options like a jumping mechanism, for example, to do away with the need of that submerged slope, which would definitely add to HAMR’s versatility.

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