Programmable matter: MIT building self-assembling robots for space

programmable matter robots

MIT scientists are building ElectroVoxels, small, smart, self-assembling robots designed for space.

It’s programmable matter, infinitely recyclable large-scale 3D printing, if you will, and it could be the future of robotics and machinery in space. In this TechFirst, I chat with MIT CSAIL PhD student Martin Nisser about building swarms of tiny configurable robots.

“Rather than building a robot or a structure in a top-down manner, we envision robots or structures as these modules of hundreds or thousands of small components or modules that can rearrange themselves with respect to their neighbors,” Nisser says.

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The mini-bots don’t have actuators: they use “small, easily manufactured, inexpensive electromagnets into the edges of the cubes that repel and attract, allowing the robots to spin and move around each other and rapidly change shape.”

Check out the story on Forbes, or keep scrolling for full video, interview, podcast, and transcript …

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TechFirst podcast: programmable matter, configureable robots


Transcript: MIT is building reconfigurable robots for space

(This transcript has been lightly edited for length and clarity.)

John Koetsier: If you’re going to space, do you want one robot or a hundred? How about a thousand? With new technology designed and demonstrated by MIT scientists, maybe you don’t have to choose.

They’re called ElectroVoxels, and they’re tiny, reconfigurable components that you can program to separate, join, change shape, even size, and perhaps … live in. To find out more, we’re joined by MIT PhD student Martin Nisser.

Martin, welcome to TechFirst.

Martin Nisser: Thanks so much. Thanks for having me. 

John Koetsier: Hey, super pumped to have you. What are ElectroVoxels? 

Martin Nisser: Yeah, so the ElectroVoxels are essentially a system of reconfigurable robots.

So it’s this idea sometimes known as programmable matter or reconfigurable robotics, where, rather than building a robot or a structure in a top-down manner, we envision robots or structures as these modules of hundreds or thousands of small components or modules that can rearrange themselves with respect to their neighbors.

And through this kind of reconfiguration, they can acquire some kind of 3D target geometry. So, essentially it’s a way to kind of think about how modules can assemble themselves in that kind of bottom-up way in order to acquire a 3D shape. 

John Koetsier: So you’ve talked about robots, maybe configurable robots, maybe even structures. What do you think you can build with them? What do you see as being possible? 

Martin Nisser: Yeah. So, generally, one of the big kind of grand challenges with reconfigurable robots is that if you want each of these small modules to be able to move by itself, you have to embed computation, electronic sensors, actuators into every module, and that’s really hard to do as the modules get progressively smaller. And you want the modules to be very small and very numerous in order to create high resolution structures.

And so, to date, it’s been very difficult to achieve reconfiguration at the module level because you have to integrate these complex, large, expensive motors into each module.

So the kind of key technical contribution that we’ve developed is to figure out a way to embed electromagnets into these modules in order to perform the reconfiguration … which is good, because these electromagnets are really, really inexpensive, they’re easy to manufacture, and they don’t require much maintenance.

And so what we’re hoping to do is to be able to use these to develop structures and robots that can actually be built scalably, so we can build these voxels — these ElectroVoxels or modules — in very, very large numbers in a way that couldn’t perhaps have been done before. 

John Koetsier: Cool. It’s interesting that you chose voxels, of course, because that’s like pixels but volumetric pixels, right? So it’s pixels in space which makes a lot of sense here.

How will you power them? Will there be solar? Will there be other sources? 

Martin Nisser: Yeah, exactly. So the point you’re alluding to is that one of the first kind of deployments we’re hoping to do with these is in a space environment, because reconfiguring here on earth against gravity is really challenging, particularly with electromagnets which are inherently quite weak. And so we’re hoping to deploy them in a microgravity setting in space.

And the particular application we’re thinking of is to be able to reconfigure large space structures in order to adapt to different load conditions or scenarios. One thing you might want to do is change structures and nurture properties, which is kind of the dynamics that govern how easy it is for structure in space to rotate.

John Koetsier: Yep.

Martin Nisser: And you might want to rotate an object in space in order to align it with incoming solar irradiation, for example. 

John Koetsier: Interesting. Or you might want to align your mass a little differently if you’re going to maybe initiate spin or something like that for a form of artificial gravity. 

Martin Nisser: Yeah, exactly. I think that’s a great example. I think there’s a lot of kind of exciting scenarios that we envision a little bit down the line, a couple years down the line. And so we’re hoping to be able to incubate this technology in the years to come in order to get it to those. 

John Koetsier: And that makes a ton of sense because of how you’d want to launch something and put a material through the tremendous stress of launch — you know, five Gs, eight Gs, whatever it might be — is very different from how you want to maybe use it in, as astronauts or working there, or as it’s doing its mission in space.

Talk about the different components that you envision. So, obviously these are voxels, they take up a certain amount of space. You might even have different size ones at a certain point, but do you have an idea for what you might do?

Will some of them have tools? Will some of them maybe have storage? Will some of them have power? Will others carry resources, like maybe metals or components or something? Maybe some are even hard or others are soft if you’re going to build internal surfaces that people might want to sit on or lean against or build upon or something like that.

What are your thoughts there? 

Martin Nisser: Yeah, that’s a great question. And the kind of the fact that you started your question with this problem that you, if you want to be able to use something in space, you don’t necessarily want to have to design or build it such that it can withstand, you know, nine Gs on launch. And you also hopefully want to build something, so … if I dial back for a second, everything you want to launch to space has to fit within the confines of a rocket fairing.

John Koetsier: Yep.

Martin Nisser: And so if you want to build something that’s wider than that rocket fairing, let’s say it’s three meters, you have to be able to package it down or disassemble it and have it deployed, self-assemble itself folded in space. And so, I think primarily we’ve been working on kind of developing the actual electromechanical system that’s capable of doing the reconfiguration.

And so in terms of applications, like the ones that you suggested, I think those are really great ideas. And what we’ve primarily been focused on is kind of the utility you get from the actual reconfiguration.

And so if you were able to, so for example, right now, we’re working on miniaturizing these modules in order to get a little bit smaller, and you want to build hundreds of thousands of these that can do reconfiguration in order to enable a kind of recyclable 3D printing.

So you can imagine being able to have a system of modules acquire a shape, and then when you’re done with that shape have it be able to reconfigure into another target shape. 

John Koetsier: Wow.

Martin Nisser: So, and so the utility of the system really comes from the actual shape that you’re acquiring. But I think that’s probably, you know, the utility of that really comes out of having a large number of modules having them very small. And so, exactly to your point, it’s a long way of answering, which is to say that you’re asking exactly the right question.

So, in the interim, we definitely want to focus on applications that can embed utility into each of these modules. So, for example, you can imagine using them as kind of self-sorting storage containers, or to think of these modules in a larger setting as being … trying to think of them as habitats for storing various items inside of them. Yeah, it’s exactly the right question to be asking.

John Koetsier: Cool.

Martin Nisser: Yeah, but so far we’ve really only been concentrating on developing the kind of key technical diffusions for them. 

John Koetsier: Do you happen to have one of the prototypes with you right now? 

Martin Nisser: Yeah. So this is one of the modules in my hand … so it’s a cubic structure. It’s about 60 millimeters in the side length and it has an electromagnet embedded in each of its 12 edges. Then in the center it has a few printed circuit boards and batteries where the printed circuit boards primarily house a microcontroller and what’s called H-bridges, which are integrated circuits that allow you to regulate the direction in which you apply current through an electromagnet.

And so what that lets us do is to determine … rather, apply to select pairs of electromagnets that will attract or oppose each other in order to actuate a pivoting mechanism. So the way an electromagnet works is that if you apply current down one way, it’ll polarize the electromagnet in a particular polarization. And if you apply it any other way, it will polarize it in the other way.

John Koetsier: Mm-hmm.

Martin Nisser: If you imagine two of these cubes next to each other, you can imagine having a pair of electromagnets, one in each module, and firing current through each of those in different directions. And that way you can imagine these as like a north-facing magnet pointing one way and the other north-facing magnet pointing the other way. And because they’re oriented like this, so one attracts.

So those create the hinge for a pivoting mechanism. And then you could take another pair of electromagnets and pulse current through them in parallel directions, and that will create a repulsing force which will actually actuate the pivoting mechanism.

John Koetsier: It’s really interesting actually, and I’ll show some of the footage that you have — you took a parabolic flight, so you experienced null gravity essentially and did some testing there, and I’ll show that — and it’s quite interesting when you’re in actual null-G, perhaps in orbit or elsewhere, it’d be interesting to see what you could design into the system.

Because what you’ve done so far is when they’re connected and then they transform and move around in a variety of different ways, with a true and lasting null-G environment, you might even be able to do it when they’re not connected and have more complex ways of fitting pieces and components together. Be that as it may, maybe talk a little bit about the testing you’ve done so far and what you’ve been able to learn. 

Martin Nisser: Yeah. So, I can start by saying that there was some scientists that developed some algorithmic work that showed that if you have a 3D structure and it’s comprised of cubes — so they’re the same way that we’ve envisioned these, the structure made up of our cubes — so if you have the 3D structure made up of cubes, they’ve shown that if each of those cubes can pivot with respect to their neighbors you can actually reconfigure your first 3D structure into any other arbitrary 3D structure … conditioned on the fact that you’re able to do two key motion primitives.

And so, that is to say, there are two movements you need to be able to do in order to do these arbitrary reconfigurations. So one is that two cubes, if you imagine them pivoting with respect to each other, you need to have two cubes that can pivot around a shared axis. And then in the second maneuver … we call it a traversal, so if you imagine I have two cubes in my hand, and then I want a third cube to be able to move from one face on one of the cubes onto the other face of this neighbor cube. And so if you’re able to do these two maneuvers, the traditional pivot and the traversal, you can reconfigure between these arbitrary shapes.

And so the kind of main piece of work we wanted to do was to show that using this particular physical instantiation of pivoting — so, using electromagnets — that we are able to demonstrate these two pivoting maneuvers, which lets us basically use their really great algorithms and deploy them on our physical systems. And so what we did was we got an air table, which is like an air hockey table, if you’ve used…

John Koetsier: Yes.

Martin Nisser: …one of those games. So it’s, people who might not know, it’s basically just a flat table that shoots air out of little holes in the surface and it creates like a very low friction environment. And so we put our tubes on this table and using the air table, we’re able to simulate a microgravity environment because it’s just very, very low friction. And so we deployed cubes on the air table and performed these two maneuvers: the pivot and traversal.

And we ran that a bunch of times and made sure that the control procedures were robust. And once we had perfected the maneuvers themselves and then the control policies, we flew the system on a parabolic flight and demonstrated the same maneuver in zero-G. 

John Koetsier: Nice.

Martin Nisser: And that was really important because on the actual flight you have just a couple of seconds in order to get it right. And so you really cross your fingers and hope it works. 

John Koetsier: Absolutely. And it’s not cheap, I’m assuming, either, to get that done. It’s called the ‘vomit comet’ at least in some instances of it, and I’m glad you were able to figure out that it did work.

It’s kind of interesting for me because my son is graduating this year in Mechatronics at the University of British Columbia, and he’s doing a capstone project — a robot arm for the Lunar Gateway. So they’re working on a design for that, they’re building a few things. They’re working with, I believe MDA, which is the Canadian space company doing that project. So, hopefully some of what he’s building gets in there. Maybe I should tell him to make it configurable … we’ll see about that, but maybe that technology is a bit out there. Look forward if you will for me about five years, what do you see these ElectroVoxels doing and being capable of? 

Martin Nisser: Yeah. So, well I think space is a great environment to have reconfiguration and particularly to use electromagnets. So, to just unpack that, so … the reason space is good is … things are difficult to build. And things get more difficult to build if they are in harsh environments, if it’s difficult to get there, and if it’s difficult to ship things there. So space is kind of like, it’s kind of the final frontier of fabrication. It’s very, very challenging to build things there. So if you’re able to have things self-assembled without the need to send astronauts up there — which is very dangerous — and to ship everything in one go, that is really advantageous. And kind of paradoxically, while it’s an environment where reconfiguration is so advantageous, reconfiguration is actually in a way, much simpler … because in a microgravity environment, you don’t have to fight gravity vectors. So even a very, very small force can generate very, very large velocities. So, figurative speaking, if a mosquito landed on a spacecraft, then just the fact that it landed there would actually accelerate it a little bit.

John Koetsier: But did it land at lightspeed? [laughing]

Martin Nisser: Well that’s … have to be another podcast for that question. 

John Koetsier: Yes, exactly.

Martin Nisser: But, so the space environment is fantastic. I think that’s really, we definitely want to explore that. But one of the things we’re looking at a little bit closer to home is — and I mentioned this briefly, earlier — is to try to miniaturize these, and we actually want to try to do reconfiguration against gravity, here on earth. And so we’re looking at trying to make these as small as possible and also to optimize all the parameters that go into the electromagnets themselves.

So in terms of the geometrical designs, the way we design the materials, the coil and winding number, the current we use … trying to optimize everything to generate as much force as possible for as small a mass as possible, in order to make them as powerful and light as necessary to be able to move them against gravity. I’m really excited about that, I think. 

John Koetsier: That is really interesting actually, because the smaller you make them the easier it is, as a percentage, I guess, to make them reconfigure against gravity, right? Mass decreases by a cube function, I believe, or as you make things smaller. So that would be super, super interesting.

And as you make them tiny enough, I mean, you get to that point where you almost have, like you said, this smart matter, this reconfigurable matter, right, that you can just reassemble continuously. And also if you make them small enough, you might even be able to power them off of, I don’t know, radio waves or something like that, or who knows what. I know some tiny little Bluetooth tags are being powered off something like that, and that’s a small amount of energy, but it’s ambient and in some environments maybe it’s not ambient, maybe it’s intentionally beamed there as well, so … very interesting stuff.

Martin, thank you so much for your time. 

Martin Nisser: Thanks so much for having me.

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