As an actuator expands, the kirigami cuts pop out and propel the robot after deflation. Source: Harvard Because nothing beats creating robots from our nightmares, a group of researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have bid to outdo the cockroach robot with one that looks and acts like a snake.
The soft robot uses the principals of locomotion of the feared reptile to crawl without any rigid components. The scales are made using kirigami — an ancient Japanese paper craft that relies on cuts, rather than folds as in origami. We have already seen researchers create a number of innovative robots inspired by origami, including those to give them muscle-like actuators, recycled exoskeletons and reconfigure into 3D shapes.
However, using kirigami has not been used as widely up until this point. As the material stretches, the flat kirigami surface is transformed into a 3D-texture surface that grips the ground much the same way a snake does.
"There has been a lot of research in recent years into how to fabricate these kinds of morphable, stretchable structures," says Ahmad Rafsanjani, a postdoctoral fellow at SEAS. "We have shown that kirigami principles can be integrated into soft robots to achieve locomotion in a way that is simpler, faster and cheaper than most previous techniques."
How They Did It
Researchers created the robot using a flat plastic sheet that was then infused with an embedded array of centimeter-scale cuts from a laser cutter. Once cut, the researchers wrapped the sheet around a tube-like elastomer actuator that expands and contracts with air like a balloon.
As the actuator expands, the kirigami cuts pop-out forming a rough surface that grips the ground. As it deflates, the cuts fold flat, propelling the crawler forward. The team was able to build an untethered robot with integrated onboard control, sensing, actuation and power supply packed into the tail.
Before choosing the snake shape, researchers experimented with various other shapes including triangular, circular and trapezoidal. They found the trapezoidal shapes resemble the shape of snake scales and gave the robot a longer stride.
Researchers believe the robot could open new avenues of design for soft robot crawlers that could travel across difficult environments for exploration, inspection, monitoring and search-and-rescue missions. They could even eventually perform complex, laparoscopic medical procedures.
"We show that the locomotive properties of these kirigami-skins can be harnessed by properly balancing the cut geometry and the actuation protocol," Rafsanjani says. "Moving forward, these components can be further optimized to improve the response of the system."
