Researchers from University of California, Berkeley (UC Berkeley), taking inspiration from the Pacific mole crab (Emerita analoga), have developed a burrowing robot for future applications such as evaluating agricultural site soils, collecting marine data and studying soil and rock conditions at construction sites.

Mimicking how the Pacific mole crab buries itself in the sand, the researchers developed the digging robot dubbed EMBUR (EMerita BUrrowing Robot), which can self-burrow vertically. The design of EMBUR’s legs enable this downward, burrowing motion, according to its developers.

1 / 1A look inside the mole crab-inspired robot EMBUR. Images show the cuticle design that keeps out sand grains and a retractable fabric leg design that enables vertical burrowing. Source: Laura Treers

To overcome the challenge of moving downward through sand-like media and soil wherein the deeper an animal digs, the harder the grains resist, thereby preventing excavation, the researchers developed a vertical-legged burrower featuring anisotropic force response. This means that the legs encounter significantly greater force in one direction than another.

"We used a modeling technique known as Resistive Force Theory [RFT] to model the forces experienced by the legs throughout their sweeping trajectories," the researchers said. "RFT helped us understand the kinds of robot geometries and behaviors that would allow for the most successful burrowing."

Additionally, the researchers devised a method for preventing sand grains from entering the robot's mechanisms and jamming them — turning again to the Pacific mole crab for inspiration.

"We created a cuticle, which is analogous to the arthrodial membrane found on the mole crabs," the researchers explained. "It's a soft, flexible material that lines the openings of joints to prevent grains from getting inside but still allows free movement."

The team intends to improve the design of the burrowing robot to allow for deeper digging, eventually enabling the robot to dig in real beach settings.

The research is detailed in the article, Mole crab-inspired vertical self-burrowing, which appears in the journal Frontiers in Robotics and AI.

For more information on the burrowing robot, watch the accompanying video that appears courtesy of UC Berkeley.