There’s an old adage that says, “Where there’s a water source, there are pests.” Indeed, that is true, especially for cockroaches. I’m not really sure if you’re aware, but a cockroach can survive underwater for up to 30 minutes. It’s one of their coolest attributes.
Now, researchers at Harvard University decided to draw inspiration from that attribute and create a robotic cockroach, which is called Harvard’s Ambulatory Microrobot (HAMR), with the ability to walk on land, swim on the water surface, and walk underwater for as long as required.
The Harvard’s Ambulatory Microrobot, or commonly known as HAMR, weighs a measly 1.65 gram and is tremendously small. Despite that, it can carry 1.44 gram of extra weight without sinking. In fact, the robot’s size is the foundation of its operation. If it were bigger than it is now, it would have been difficult to support the robot with surface tension. On the other hand, if the robot were smaller than its current size, it might not be able to produce adequate force to break the surface tension.
The Technology in HAMR
To learn more about what makes the HAMR work, here is an explanation from The Harvard Gazette: “The HAMR makes use of multifunctional foot pads that rely chiefly on surface tension and surface tension-induced buoyancy when it is time for the HAMR to swim, but it can also apply a voltage to break the water surface when it is necessary for HAMR to sink. This procedure is known as electrowetting, which is the reduction of the contact angle between a material and the water surface when a certain voltage is applied.”
The HAMR’s multifunctional feet, which actually gives it its terrain flexibility, is made of electrowetting pads (EWP). The goal of electrowetting is to reduce the surface tension in a liquid-solid interaction by means of electricity. That is to say, an electric charge makes it possible for materials to break a water surface.
With the robot’s electrowetting pads underwater and activated, the HAMR is able to move across the water surface. Having four pairs of asymmetric flaps and customized swimming gaits, the HAMR propels in a manner that is quite similar to a diving beetle.
Rooms for Improvement
Now, one of the major hurdles for the engineers was getting the HAMR to move from walking underwater to the surface again. The issue was with the water tension since it would weigh down on the tiny HAMR with a force twice its weight.
The answer to that problem was to stiffen the robot’s transmission and to install soft pads on HAMR’s front legs, mainly because the new pads allowed for friction redistribution. Doing all of that enables HAMR when treading slowly up a small underwater slope, to penetrate the surface and walk onto dry land.
Kevin Chen of the Harvard Microrobotics Laboratory stated that they are looking forward to the day that these HAMR robots could eventually be used in rescue and emergency situations. Indeed, it is quite possible that it could happen, and it might just be sooner than we think.