Researchers at New York University’s Tandon School of Engineering have developed WorMa, an amphibious robot inspired by worms’ adaptability. Designed for rugged coastal terrain, it traverses rocks, slopes, and steps while also entering and exiting water. Rather than mechanically reconfiguring its body for each environment, WorMa maintains a basic undulating movement and redistributes its weight. The five-link, four-joint robot measures about 20 inches and weighs slightly more than 2.2 pounds.
A central pump transfers approximately 300 grams of water between latex balloons in its head and tail, using the liquid as movable ballast. Loading the head increases force at the front contact points, improving traction. In tests, this configuration enabled WorMa to climb a 19.5-degree incline, whereas alternative weight distributions caused backward sliding. It also reduced the energy cost of travel by at least 33 percent. In water, shifting weight toward the tail produced swimming speeds up to 26 percent higher and efficiency 52 percent greater than the head-heavy configuration.
To negotiate steps, WorMa approaches head-heavy, shifts water backward to raise its front, then transfers it forward again after contacting the edge. This sequence allowed it to clear steps up to six inches high. A head-heavy configuration also provided the traction needed to leave water by pulling onto a slope. Demonstrations combined flat ground, a step, a slope, and open water. Potential applications include environmental monitoring and infrastructure inspection. The researchers are developing faster pumps and sensor-based controls that could detect terrain changes and automatically redistribute weight.
