The project was novel because it demonstrated that sophisticated mobile robots can be engineered at very small sizes by taking a page out of nature's book.
Now SEAS Professor Robert Wood and his team are back.
This time they've outfitted their creation, dubbed the Harvard Ambulatory Microbot (HAMR), with special feet that give it the unusual ability to walk on water or dive beneath the surface.
According to a recent paper in Nature Communications, the feet are four asymmetrical flaps that spread HAMR's roughly two grams over enough area that no one foot will break the surface tension of the water.
The robot "walks" by shimmying its legs at a frequency of up to 10Hz, as illustrated in the embedded video. It can carry an additional payload nearly equaling its own weight, which means it could be equipped with sensors down the road.
When the robot needs to sink, it applies voltage through its feet to break the surface tension. After it settles on the bottom, it walks just as it would on land.
The same surface tension that holds the robot up became a challenge for the team when they realized early versions couldn't break through the surface from below when trying to climb out of the water on an incline.
They tackled the challenge by stiffening up the transmission and installing new pads on the robot's front legs to give more friction against the bottom.
That's resulted in a more capable robot roach, as well as some cocked eyebrows from those uncomfortable with the cockroach army taking shape.