Building a robot is hard. Building one that can sense its surroundings and learn to move on its own is even more difficult.
But the UCLA engineers took on an even bigger challenge. Not only did they create autonomous robots, but they 3D printed them in one step.
Each robot is about the size of a finger. Their bodies resemble a bamboo mat folded into an N shape, and they glide at speeds of up to 25 feet per minute.
What made the feat possible was the invention of a new type of all-in-one material that is able to bend, twist, flex and stretch.
“The traditional robots you see today rely on several different components,” said Rayne Zheng, a mechanical engineer and project leader. The body of the robot, its moving parts and its electronics have to be built separately and then assembled together. “With 3D printed materials that can be robotized, we don’t need any of that.”
The breakthrough, described last month in the journal Science, paves the way for inventions ranging from nimble rescue robots capable of navigating tight spaces to sensitive prostheses with fewer parts to break.
UCLA researchers have developed materials that allow small robots to become autonomous after receiving basic commands.
“A lot of times, 3D printing is used as a novelty to generate publicity … but that’s not the case here,” said Ryan Sochol, a robotics engineer at the University of Maryland who was not involved in the study. . .
Robert MacCurdy, who designs automated robots at the University of Colorado Boulder, called the UCLA work “a true breakthrough in 3D printing technology.” He said the printing of a shape-changing mobile material with embedded electronics and remote sensing capabilities had not been achieved before, and it heralded “the production of robots in the future”.
Zheng and his colleagues undertook the project three years ago to see if they could use 3D printing to build a material capable of sensing its environment, for example measuring the surrounding temperature and noticing whether it has been hit or crushed. .
Once that goal was accomplished, they added another. “We started to think, in addition to intuiting, why not make it move?” Zheng said.
And they still wanted to do it all in one step.
Ordinary 3-D printers work like a machine that adds icing to a cake. They build thin layers of plastic, metal, glass, or other materials to produce an endless list of products like jewelry, tools, prosthetics, and even pizza. But they can only print one component at a time.
To print an entire robot at a time, Zheng and his colleagues needed a versatile material. So they created one of silicon carbide, which supports the structure of the robots; electrodes made of copper and gold, which carry current; and piezoelectric ceramics, which change shape in response to an electric field.
Each part contributes to an entirely new “metamaterial” that can bend and flex, stretch and squeeze, and twist and rotate, said Huachen Cui, a postdoctoral researcher in Zheng’s lab who led its development. And the metamaterial can be 3D printed in one go.
The new material required a custom 3D printer, so the team built one that takes up the space of an office desk. Its operation is similar to freezing a design in a glass of water and draining the rest, leaving behind an intricate ice sculpture. But instead of water, the printer alternates between vats of the three ingredients, then uses ultraviolet light to solidify each layer of the metamaterial web as the robot takes shape.
The result is basically like a muscle. “It has everything integrated, from structural components, sensing components, to motion and electronic control,” Zheng said.
In other words, MacCurdy said, it’s a truly functional object: “When it comes out of the 3D printer, it requires no additional assembly.”
Cui put it on a robot by placing it on a table between a pair of pipes. A set of cables tied the robot to a power source. When the power was turned on, the robot came to life with an unusual bright green flash accompanied by wisps of smoke. But soon it moved with the soft hum of an electric shaver.
The three parts of his N-shaped body form a muscle that flexes faster than the eye can discern, propelling him forward with ease. It can even jump over small obstacles of about 1 millimeter in height.
The design was inspired by nature.
“I wanted to make it nimble and very fast; the first thing I could think of was a leopard,” said Cui, who was the lead author of the study. “Just hit the ground and move on. That’s it.”
Robots rely on ultrasound to sense their surroundings, like bats. But instead of using echolocation, the machines use a 3D-printed remote sensor that bounces radar pulses in various directions. The way they recover alerts the robot to obstacles in its path so it can adjust accordingly.
The machines, which are small enough to fit on a dime, can support more than 13 times their own weight. When Cui loosened a bolt in a basket attached to the top of the robot, it shook and began to move faster. The impact, meant to mimic falling debris, was his cue to make a quick escape, he said.
Zheng said it wouldn’t be difficult to make the robots bigger — all they would need is a bigger 3D printer. The real challenge is to make the robots smaller and able to operate in water.
This is something that excites Sochol.
“I think biomedical applications, particularly drug delivery, is an application where it could really have a legitimate use,” he said. He envisioned a scenario in which a small robot carries a dose of medicine to a specific location in a blood vessel. Once it’s in position, doctors could “shock it with an electric field” to release its payload.
Zheng’s lab is already equipped with a small tank on the ground to test a future generation of aquatic robots. If a leopard inspired the original version, the new ones will be designed to mimic the swimming and crawling abilities of shrimp.