A soft robotic hand has finally completed a historic feat: beating Super Mario Bros.’ first level.
Although fast pushing and releasing the buttons and directional pad on a Nintendo Entertainment System controller is a fun way to assess the machine’s performance, the actual innovation is in how it was designed.
The Mario-playing hand, as well as two turtlelike “soft robots” disclosed in the same Science Advances study, were all 3-D printed in a single procedure that took only three to eight hours.
According to co-author Ryan Sochol, an assistant professor of mechanical engineering at the University of Maryland, “every single one of those robots in this work was 100% no-assembly-required-printed.”
Researchers would find it easier to construct increasingly complex soft robots if they could produce them in one step.
The squishy nature of these bots allows them to interact with sensitive materials, such as tissues in the human body, without causing the kind of damage that more rigid machines might.
This qualifies them for jobs such as surgery and searches and rescue, as well as sorting fruit and other easily damaged things.
However, most of these bots still include at least some rigid components.
Researchers didn’t make one totally out of flexible materials until 2016.
The inventors of the octopus-like soft robot had to forego rigid electronic circuits in favor of a microfluidic one to make it operate.
Water or air flows through microchannels in such circuits, with fluid-based equivalents to electronic components like transistors and diodes modifying its flow.
The researchers in this recent study have accelerated the development of this technology.
Jennifer Lewis, a Harvard University engineering professor who co-authored the 2016 study but was not part of the University of Maryland project, adds, “They introduced considerably more sophisticated microfluidic circuits.”
The circuit in the Mario-playing hand, for example, allowed a single supply of fluid to deliver several messages.
Changing the input pressure allows you to tell each finger to move separately.
GETTING IT PRINTED
Fluidic circuits make soft robots more intelligent, but they also make them more difficult to manufacture and assemble.
That’s why Sochol is so enthusiastic about printing them all at once. “To have a full soft robot with all of the integrated fluidic circuitry, the body features, and the soft actuators [moving components] all printed in a single run has never been done before,” he says.
He and his colleagues used a PolyJet 3-D printer, which lays down a liquid layer, then exposes it to light to solidify it before adding the next layer.
The model they used, developed by Stratasys, could produce three different types of material: a rubbery, squishy substance
a more stiff plastic-like one, and a water-soluble “sacrificial substance” that serves as scaffolding during printing but must be removed afterward.
These high-tech printers can cost tens of thousands of dollars, but Sochol’s team did not require one.
He explains, “We employ a service on campus to achieve this.” “So we emailed them our files, they printed it, and we picked it up.”
Anyone else who wants to print one of these designs—which his team provided as open-source software on the development site GitHub—could do so for around $100 or less using a similar 3-D-printing service, according to Sochol.
Sochol claims that this method is faster, cheaper, and simpler than producing a microfluidic circuit in a clean environment, building a robot separately, and then putting them together later.
Lewis isn’t quite convinced. “It has a certain grace about it. “I’m not convinced it’s necessarily faster or cheaper,” she says.
“However, having to design the circuit one way and then install it into a molded and 3-D-printed robot, as we did, is inconvenient. And I’d argue that the approach [Sochol and his colleagues] picked… has a lot of advantages in terms of being able to print a variety of stiffness materials.” Lewis also mentions that the new soft bot isn’t ready to use right away after being printed.
“One of the more time-consuming aspects of their process is having to remove all of the sacrificial material,” she explains.
“And when it’s only for support on the outside of the body, that’s OK. However, it’s there in all of those internal routes as well.”
MARIO, IT’S ME!
Sochol’s team had to build a performance test after cleaning up their printed robots.
Previously, robotic fingers had been designed to play a piece on a piano, but Sochol’s team decided that challenge was too simple.
“We could set the tempo arbitrarily with that,” he explains. “There are no real penalties if the robot misses a note or something like that.” Video games appeared to be a little more ruthless.
“If you make a mistake, if we don’t push the button at the correct time or [release] the button at the right time, you can run into an enemy, fall a pit, and it’s an instant game over,” Sochol explains.
The researchers used a Nintendo controller with their three-fingered robotic hand, each finger on a distinct button or directional pad.
They could make each finger respond by sending fluid through a control line at varied pressures.
Sochol says that when the pressure is low, the circuit can respond by pressing only the button that enables Mario to move ahead.
“After that, a second finger begins to push a button with medium pressure, and Mario can now run.”
Then, if there’s a lot of pressure, Mario will jump because all three fingers will be touching their respective buttons.”
The team created a computer program that would automatically vary the pressure, forcing the fingers to move in a predetermined pattern.
The developers knew exactly what sequence of buttons the hand would need to hit to win the game’s first level because people have been playing Super Mario Bros. for decades.
It only had to cycle through the preprogrammed list in the exact order, which is more difficult than it appears.
“Getting it to not simply push a button and then stop pressing it and then repress it, because there are a lot of occasions where Mario has to jump and then jump again very quickly as he runs,” Sochol adds.
“The Mario portion is kind of charming and will get attention,” Lewis says.
“However, I believe that the multi-material 3-D printing, and the ability to combine all of this intricate fluidic circuitry in one fab process, is what makes this paper so compelling.
There’s a lot to admire in what [the researchers] have accomplished.”
The fully printed robotic hand’s victory in the video game demonstrated its ability to respond quickly and precisely to changing input.
This point might have been made in any well-known video game, but Mario has a particular place in the hearts of many gamers.
Sochol explains, “We felt like this was the baseline game.” “When we acquired a Nintendo system when I was four or five years old, that was the first game I ever played.”