This Cockroach-Inspired Microbot Can Swim, Sink and Walk Underwater

This microbot can swim on the water surface, break the surface tension to sink and also walk underwater.

Cockroaches are generally known to survive for about 30 minutes underwater. However, a robotic cockroach can now do one better. Harvard’s Ambulatory Microrobot, otherwise known as HAMR, can swim on the water’s surface, walk underwater and also walk on land for as long as it wants. This has opened up novel environs for HAMR to explore.

The way the next-gen HAMR works is quite simple. When HAMR wants to swim, it utilizes multifunctional foot pads that are reliant on surface tension and its induced buoyancy.

That said, if HAMR wants to sink underwater, it can even apply a voltage in order to break the surface of the water. This entire process is known as electrowetting.

It is a process in which the water surface and the material experience a reduction in the contact angle when a voltage is applied. It is precisely due to this modification of the contact angle that makes it possible for objects to sink beneath the surface of the water.

A MicroRobot can reduce drag and evade submerged obstacles when walking on water’s surface. HAMR robo-paddles utilize four different pairs of asymmetric flaps in addition to customized swimming gaits so that they can swim on the surface of the water.

The robot also creates its swimming gaits much like the diving beetle, making full use of the unsteady interaction between the passive flaps of the robot and the water surrounding it.

As a result, the robot is able to swim in a forward motion and turn effectively. The first author of the paper and a postdoctoral fellow at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), Kevin Chen said, “This research demonstrates that micro-robotics can leverage small-scale physics — in this case, surface tension — to perform functions and capabilities that are challenging for larger robots.”

The most updated research of this theory has been published in Nature Communications.

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“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,” added Neel Doshi, co-author of the paper and a graduate student at SEAS.

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HAMR weighs as much as a reasonably large paper clip (about 1.65 grams), can paddle the legs at a frequency of 10 Hz and can carry an additional payload of 1.44 grams without sinking. The topmost coat on HAMR is of Parylene. This prevents the robot from shorting underwater.

“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,” said Robert Wood, senior author, Charles River Professor of Engineering and Applied Sciences at SEAS and core faculty member of the Harvard Wyss Institute for Biologically Inspired Engineering.

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The researchers hope to be able to enhance the locomotion of HAMR further and find a plausible way for it to return to land sans a ramp. They plan to do this by incorporating impulsive jumping mechanisms or gecko-inspired adhesives.

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