Harvard’s Robotic Cockroach HAMR Can Walk Underwater

One of the most durable creatures on earth is cockroaches. Harvard robotics have worked with Harvard’s Ambulatory Microbot (HAMR) lab to create a custom cockroach robot. The new HAMR can walk on land, swim on the water surface, and walk underwater as long as it is needed. HAMR gets its terrain flexibility from the multifunctional feet which are made of electrowetting pads (EWP). The focus of electrowetting is to reduce the surface tension in a liquid/solid interaction using electricity. An electric charge makes it easier for the materials to break the water surface.

With the electrowetting pads submerged and activated, the HAMR can move across the surface of the water. It has four pairs of asymmetric flaps and custom-built swimming gaits. The HAMR paddles in such a way which is similar to a diving beetle. Neel Doshi, a Harvard grad student said, “HAMR’s size is key to its performance. 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”.

The HAMR cockroach weighs only 1.65 grams. This weight is equivalent to a large paper clip weight. It can also carry a weight of 1.44 grams on its back before drowning. One of the biggest challenges for the engineers was to get the HAMR to move from walking underwater to the surface again. The problem here was the water tension which could easily weigh down on the tiny HAMR with a force twice of its own weight. The solution came from stiffening the robot’s transmission and installing soft pads on the robot’s front legs. The new pads helped with friction redistribution. All of that allowed the HAMR to walk slowly on a small underwater incline.

Robert Wood, a senior author of the research said, “This robot nicely illustrates some of the challenges and opportunities with small-scale robots. Shrinking brings opportunities for increased mobility – such as walking on the surface of the 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”. Researchers are often looking at smaller animals for inspiration. MIT also recently developed a robotic fish that can blend in with the real thing in order to study the school patterns of fish. Scientists might have improved the cockroach’s ability to walk underwater for 30 minutes but there are still many features which have still not been captured by them.