Will a new breed of highly mobile, radiation-resistant soft robots become automated work horses for the nuclear industry—or save the day during nuclear disasters? A team of graduate students wants to make sure they’re up to the task.
NPR NEWSCAST MONTAGE: As we’ve just heard, the problems at the nuclear power plant in Fukushima, Japan, are growing more ominous. There was a third explosion and a fire and there are more reports of high radiation levels… First there was the earthquake, then the tsunami, and now the crisis in Japan is only getting more complicated… The intense radiation inside the reactor buildings means it’s too dangerous for workers to enter. But a small team of American robots is getting ready to go in.
[MUSIC: Wounded, by Kevin MacLeod, used with permission under a Creative Commons Attribution 3.0 Unported License]
STEVE FRANDZEL: On March 11, 2011, the terrifying prospect of nuclear disaster became real when Japan endured a magnitude 9.1 earthquake struck Japan. Next came a 15-meter tsunami, which overran the Fukushima Daiichi nuclear power plant situated right up against the east coast. Fuel cores melted down, hydrogen gas explosions blew out roofs and walls, and high levels of radioactive elements were released into the air and sea. It remains one of the worst nuclear disasters in history and will take decades to clean up. But this podcast is not about Fukushima. Well, it is, and it isn’t. It’s really about robots. Not the rigid robots we’re accustomed to, but soft robots. It’s just that Fukushima presented an extreme and stark test where the limitations of robotic technology were on display, and it wasn’t pretty, as you’ll soon see. A robotics engineer at the NASA Jet Propulsion Laboratory said this about the disaster: “What would have been really great is if we could have sent robots in to do something as simple as turn a valve.” What if there had been a different type of robot? A soft robot as supple and pliant as skin and muscle, which moves fluidly and navigates naturally and easily through debris and confined spaces. They’re resistant to the high radiation levels. Maybe one of them could have found the missing fuel core that had melted its way through the containment vessel. Maybe another could have found and plugged leaks in one of the buildings where high levels of radionuclides were leaking into seawater. And maybe workers would have been exposed to less radiation during clean-up operations. It’s all academic of course, and it’s lot of what ifs. But what other question has led to the attainment of so many big ideas? So on to the podcast about soft robots and a couple of grad students whose collaborative research is paving the way for these devices to withstand high radiation levels so they can work in dangerous areas of nuclear facilities — or, on a really bad day, a disaster zone.
NARRATOR: From the College of Engineering at Oregon State University. This is Engineering Out Loud.
OSMAN DOĞAN YIRMIBEŞOĞLU: So as you may know, when you say first time “robot,” people generally think about rigid robot arms that place stuff from one place to another, or that works in the manufacturing plants of the automobiles. But soft robots are the ones that are made out of silicone or the materials that are as soft as silicone itself. Hello, my name’s Osman Doğan Yirmibeşoğlu. I am from Turkey and I’m getting my robotics Ph.D. at Oregon State University.
[MUSIC: Brain Trust, by Wayne Jones, used with permission]
The beauty of soft robot technology is that it’s adaptable. Imagine an elephant trunk, so it’s just the trunk, right, it can lift heavy loads, it can be very, very gentle, it is very adaptable, it can squish around small areas, it can bend on multiple angles. So basically we are trying to mimic an elephant trunk — for example, to grasp delicate objects from one place to another, like picking a fruit from a tree or grabbing your burrito and transferring it from one line to another in a factory, or grasping your egg and placing it inside the carton. Also, we are building some soft robots that can crawl. They are very slow, but they can walk in any environment, under snowy conditions, under fire conditions, a car can go over them and they keep moving. Soft robots are harmless against humans and it is really hard to destroy them, too.
FRANDZEL: A big reason that they’re so robust and mobile is that many designs are inspired by animal locomotion — or bioinspired. They mimic, for example, the motions of snakes, fish, and the octopus. Doğan is designing a meter-long soft arm inspired by that elephant’s trunk he talked about. Soft robot technology has a ways to go before it catches up to its rigid cousins, but many of the capabilities of high-functioning robots today seemed like pure science fiction a decade ago. They hold the promise to become safer alternatives to things like those big manufacturing robots isolated in cages for safety. Running into a soft robot would be akin to colliding with another person, but being smacked by a high-speed steel arm — well, that’s killed people. Soft robots may help to restore limb movement in stroke victims, be used as prosthetics, or become a versatile tool in search and rescue operations.
[MUSIC: Impromptu in Blue, by Kevin MacLeod, used with permission under a Creative Commons Attribution 3.0 License]
YIRMIBEŞOĞLU: In the case of a collapsed building, if there’s a small hole in there, if you’re rigid robot doesn’t have the size that fits inside that hole, you cannot go in there, but you can push your soft robot and since its shape is adaptable, it will shrink and go into that hole. Can these robots rescue someone? No, but these robots can be good for observatory purposes and identifying purposes, because they can go into many areas and investigate with the cameras and sensors and come back. It’s going to take a little bit of time for them to move because they are very slow, but they are very robust.
FRANDZEL: The soft robots that Doğan works with are made of a silicone rubber called polydimethylsiloxane. It’s really squishy and kind of satisfying to play with. Good for stress relief. He makes them on a 3D printer that deposits, layer by layer, the entire robot.
YIRMIBEŞOĞLU: You just design the object in a computer program, then send it to the 3D printer, and the 3D printer prints it for you. And I’m really happy to tell you guys that in Oregon State University, we developed this 3D printer that can make this possible.
FRANDZEL: So every time you’re going to get the same result.
YIRMIBEŞOĞLU: Yes. Every time we get the same consistency, even if there is an error, that error is consistent too. It’s really great to have a 3D printer make the job for you, because you just need to design the thing and wait until your print is done.
FRANDZEL: But a lump of static silicone isn’t much of a robot. It’s a lump. To actuate a soft robot — make it move — Doğan pumps air or liquid through tubes that are connected to a network of small channels and pockets that run through the silicone body of the robot.
YIRMIBEŞOĞLU: Inside there is an empty cylindrical channel. When we push air inside it — what I mean is, when we pressurize the channel, it bends towards one side, which is thinner than the other side. Basically, we are pumping in water or air to create the motion of the soft robot.
[MUSIC: Brain Trust, by Wayne Jones, used with permission]
FRANDZEL: By regulating the pressure and adjusting the thickness of the robot’s walls, the robot can turn, crawl, raise up or down, roll, and even paint landscapes. Or maybe it’s a self-portrait. You can decide. Just click the link in the show notes on our website to watch a snake-like robot at Oregon State make art. Doğan assured me that no robots were harmed during filming. There are also some other mind-bending robot videos on tap there. Now it’s moving. But you still need to know what it’s doing and where it’s headed, because the robot will not always be in sight. This is where things get even more extraordinary, because running through the silicone body are veins of liquid metal sensors. Doğan explains it better than I can.
YIRMIBEŞOĞLU: This liquid metal is a composition of gallium, indium, and tin, so that we can keep a material liquid in room temperature. We have the liquid metal inside the silicone channels. These channels are micro channels, very small. And in the change of motion, like in the bending motion for example, those lines deform according to the bend angle, so that when a line deforms, we are able to measure the resistance of the liquid metal material, because it’s acting like a resistor. So that when we actuate the motion, we can tell that we bent it 30 degrees but we want to bend it 50 degrees, let’s give a little bit more pressure.
FRANDZEL: For now, most soft robots are tethered to their control systems, which may limit their range. But eventually, as controllers get smaller, the robots will become self-contained. The supple elasticity of soft robots — their ability to compress and stretch and twist and bend—defines their essential nature: adaptability. That quality will one day enable them to become inexpensive replacements for some rigid robots and accomplish tasks that rigid robots aren’t well-suited for. The nuclear industry has used rigid robots for years. They inspect pipes, check radiation levels, remove waste, and pressure wash contaminated surfaces, to name a few jobs. To protect the vulnerable semiconductors in their circuitry, they’re hardened — or shielded — against ionizing radiation, which adds a lot of cost and weight. But all of them go about their business in known, structured environments like hallways, tunnels and pipes, where moving around is pretty easy. Their tasks are routine and repetitive, and they’redesigned to complete specific jobs.
TYLER OSHIRO: The differences between nuclear energy and let’s say like a Fukushima-type situation is these are very different situations.
FRANDZEL: That’s Tyler Oshiro, Doğan’s research partner and a Masters student in radiation health physics in the School of Nuclear Science and Engineering.
[MUSIC: Enter the Maze, by Kevin MacLeod, used under a Creative Commons Attribution 3.0 License]
OSHIRO: In the nuclear energy field, robots are required to do very repetitive tasks that humans can’t. These are sometimes working alongside humans, sometimes independent of the humans, and the idea is to reduce dose to people by putting a robot in that task instead. But because this is an industry, there’s an established way of doing things, and so the question of adaptability doesn’t really play into that field as much as it does in let’s say a disaster type or waste scenario, where the environment is unknown. What we deal with in a lot of nuclear environments is contamination. So typically if these robots are contaminated, they can’t leave the environment. With something like a soft robot that has detachable parts, or the soft robot itself being completely 3D printed and easy to manufacture, you’d have a robot that can then be disposed of as soon as it’s contaminated after having completed its task and without a huge monetary hit to the operator.
YIRMIBEŞOĞLU: So the soft robot body will enter the high-radiation environment, and the tubing lines that are coming out of the soft robot will create a distance from high-radiation environment to low-radiation environment, and we will be able to put our controller board, which will have the semiconductors, away from the high radiation.
OSHIRO: If you could send a soft robot instead to do those sort of tedious and dangerous tasks, you would be saving the industry a lot of money. They’re relatively cheap and more disposable than traditional rigid robots. It’s not a competition between rigid and soft robots, really. It doesn’t need to outcompete rigid robots, because it would have different applications that rigid robots either can’t do or cannot perform efficiently, or it wouldn’t make sense for them to do.
FRANDZEL: So for routine work in a controlled setting, rigid robots get the job done. But what about a scrambled, broken place? Let’s return to Fukushima, a big mess and the epitome of an unstructured environment. Tokyo Electric Power, which owns Fukushima, didn’t have a single robot for disaster response — kind of surprising considering that Japan is home to a thriving robotics industry. Over a period of years, more than a dozen rigid robots went in. They all failed, sometimes within hours, either fried by the radiation or because they couldn’t get around, over, or through the physical chaos.
[MUSIC: Back Stairs, by Poddington Bear, used with permission under an Attribution-NonCommercial 3.0 International License.]
OSHIRO: These robots are typically on wheels — sort of tank-inspired wheels with the rollers. They can typically roll over different kinds of rubble, they can go up and down stairs. But in undefined environments, you really don’t know what you’re getting into. They have no way of adapting to an obstacle that’s in their way if they’re not designed to do so. So that rigid robot would have to come back out, you’d have to make some adaptations to either that robot or send in a different robot. With a soft robot, you go in, you observe, you see that this valve is left open or that this needs to be sealed, and this soft robot that is more adaptable and is inherently equipped to perform more tasks can then just go in and simply shut that valve off and come back out and saves you a whole lot of time, and it has completed the task much more efficiently and much more quickly. The idea I think, especially in undefined environments, is that it can get into the environment faster and it can shut that off more quickly, because it can adapt to the environment.
FRANDZEL: Whatever its task, the robot must function while exposed to high radiation. So Doğan and Tyler conducted a study where they subjected samples of the silicone rubber to levels of radiation that correspond to several processes in a nuclear plant.
OSHIRO: We exposed them to different doses of gamma radiation and saw how the increasing dose affected the mechanical properties. The two properties that I tested for primarily were elongation and compression, because that’s what the soft robot’s going to have to be able to do. What we were looking for was red flags, basically. If this material could not hold up under radiation at all, then there would be no path forward for soft robots in radiation environments, because gamma is one of the big components of any radiation environment.
FRANDZEL: Indeed, the radiation took its toll.
OSHIRO: So you saw less of an ability for the robot to stretch and less of an ability to compress. So you required more force to make the robot do anything. And there was a certain point, I think above 400 kiloGray, where the robot almost became a full solid at that point and was basically not operable.
YIRMIBEŞOĞLU: At this point, I want the audience to understand 400 K is a great value.
OSHIRO: Yes, absolutely correct.
YIRMIBEŞOĞLU: So that means that soft robots will withstand ridiculously high radiation environments.
FRANDZEL: They’re planning the experimental design for their next study to test how the liquid metal sensors function in a radiation environment.
OSHIRO: In the same way that we looked at the silicone rubber, look for red flags. So if the liquid metal is exposed to, let’s say, a mixed neutron/gamma environment, if it’s not going to become liquid anymore, because that would be a serious issue. So we’re starting with things that we know we can test and then moving on to things that would be more important in the final product.
FRANDZEL: Right before we finished, I brought up an article that quoted Doğan — something that prompts an intriguing image of the future, when soft robots become as pervasive and indispensable as rigid robots are today. You said it’s easy to imagine making soft robots that are ready for operation that will just walk out of the printer.
YIRMIBEŞOĞLU: Yes. Currently our team is working on a multi-material printer, which will be able to 3D print the soft robot with embedded sensors on it. So when the print is done, what we need to do is just install the tubes, and we can make the robot walk out of the print pad. It’s coming. It is soon. It’s not scary, it’s lovely.
FRANDZEL: In 2017, more than six years after the Fukushima disaster, a little aquatic robot nicknamed the sunfish sent back the first images of the fuel core from reactor number three, which had melted through the bottom of its containment vessel and disappeared. But what if there had been a different type of robot? What if…?
[MUSIC: Brain Trust, by Wayne Jones, used with permission]
FRANDZEL: This episode was produced and hosted by me, Steve Frandzel, with additional audio editing by Brian Blythe. Thanks Brian.
BRIAN BLYTHE: You’re welcome.
Our intro music is The Ether Bunny, by Eyes Closed Audio on SoundCloud, and used with permission of a Creative Commons Attribution License. Other music and effects in this episode were also used with appropriate licenses. You can find the links on our website, as well as some great videos. For more episodes, visit engineeringoutloud.oregonstate.edu, or subscribe by searching Engineering Out Loud on your favorite podcast app.
FRANDZEL: By the way, you’ve mentioned burritos four times. Will it be able to deliver burritos?
YIRMIBEŞOĞLU: I’m not sure, maybe. I will try to make an experiment with picking up a burrito and putting it somewhere else. When I’m done I will send you the video.
OSHIRO: Putting it in your mouth?
YIRMIBEŞOĞLU: Maybe, maybe.
OSHIRO: See, this will be a new avenue of research. There you go.
YIRMIBEŞOĞLU: True, true.