One could argue that nature is the world’s best designer; biomimicry is a design approach which draws on biological processes and natural entities to create products, structures, and systems. Today’s episode discusses how insect anatomy and the natural world influences and inspires Sarah Bergbreiter’s work on small robots. As she creates robots just a few millimeters long, Bergbreiter utilizes nature as her bioinspiration.
In this episode, Bergbreiter discusses her research on small robots, as well as sensors and actuators which improve capabilities of larger robots. She discusses the physics and chemistry required to optimize these small robots, as well as potential applications of this technology. This technology, she discusses, could be used in many fields, from medicine to ecology.
For more information, visit https://www.meche.engineering.
Richard Jacobs: Hello. This is Richard Jacobs with the future tech and future tech health podcast. I have Sarah Bergbreiter. She’s a professor of mechanical engineering at Carnegie Mellon. And we have been talking about her work and research and other stuff like that. So Sarah, thank you for coming.
Sarah Bergbreiter: Thanks for having me.
Richard Jacobs: Tell me about your research and then maybe we’ll go a little bit back into your origins.
Sarah Bergbreiter: Sure. So my research is primarily at the intersection of microsystems and robotics and there’s kind of two cool areas to look at there. First one, we use microsystems to actually build tiny robots. And so that goes to a robot the size of an ant that can run or walk or jump and be able to get around ultimately very tiny mobile microrobots. The second thrust is actually using microsystems to make improved sensors and actuators for larger-scale robots. And so this comes from the idea of we use a lot of microfabrication that’s based on microelectronics and memes to create very small sensors and actuators that can ultimately improve the capabilities of these larger robots.
Richard Jacobs: Yeah, I used to work at Intel and Motorola and Fab, so they would do chemical vapor deposition and etching and things like that to make computer chips on vapors. Is that what you’re talking about? To make some of these micro machines?
Sarah Bergbreiter: Yeah, very similar ideas. We tend to incorporate a lot of materials that somebody at Intel might not typically use. So things like polymers, particularly soft polymers, so things like a silicone rubber Pd.Ms. And that enables a vast kind of materials toolbox that we can draw from to make these very small mechanisms and actuators and sensors as well.
Richard Jacobs: So what’s the point? I’m making small scale robots. Would it be to put inside the human body or are there other benefits you get from having really small robots with many of them?
Sarah Bergbreiter: Yeah, that’s a great question. So one of my kind of ideal scenarios is that is just you get large end from this. You get a lot of robots and you can get a lot of really cool things if you can have a lot of robots work together. And so I kind of futuristic scenarios. You have a bucket of these small robots that you can just sprinkle over a disaster site to help find people after a disaster for example. I’d say primarily right now we use some for scientific discovery in fact. So the idea of trying to understand how things like a frog hopper insect can jump as high as they can. We actually build physical models of some of the important features of that insect and actually use that. We can change the different variables around much more easily in our robot than you could the actual insect and try to really understand what are the important parts of that make that insect jump as high as it does or some insect run as fast as it does, for example.
So we use a lot of these robots to actually better understand the world around us as it is right now and some of the organisms in that world. And then I think another potential thing that you touched on is the idea of medical devices. And so a lot of the robots that we’re talking about are not going to be, you know, you’re not going to necessarily have one injected into you and it’s going to travel through your bloodstream. Our robots are typically too big for that, so they’re on the size scale of millimeters. So more like an ant. But if you think about what a robot is, a lot of the sensors, actuators, mechanisms, computation, right? If you could stick all of that in a catheter, you could potentially do a lot more in terms of surgical procedures and you can right now and minimally invasive surgical procedures to be specific. So I think all of these different things are kind of fun ideas and important ideas for these small scale robots.
Richard Jacobs: Well, it seems like, with a really small robot, there’s a tradeoff where you have to have large numbers of them in order to accomplish a task in the macro scale and they had to be coordinated and communicated with each other. So it probably changes the dynamics of the robot in your, the communication’s probably a lot more important than maybe just the ability of one of the robots itself.
Sarah Bergbreiter: Yeah, it does. Communication is a tricky thing though. You don’t necessarily need explicit communication. So if you think of how answerable to create bridges out of themselves. A lot of that is just by sensing what their fellow ants are doing for example. And so you can have this more implicit communication between the robots to do these more complex tasks. And then in terms of kind of capabilities that you can put on these robots. We also work on slightly larger scale robots, so robots that are grams in size and then those scales you can actually put small cameras and radios and you could use those for things like inspection tasks. So send them into an area that is not easy to get into otherwise, say the jet engine, and be able to take pictures and make sure things aren’t going to fail. So there’s a lot of across the range of robots that we work on. Like there’s a fair there’s quite a range in terms of capabilities ultimately on the robots as well.
Richard Jacobs: Well, what are some of the most exciting potentials that you’ve identified? You know, you have a lot of projects, but which one do you maybe secretly hope gets there first because of the application?
Sarah Bergbreiter: Oh, because of the application is an important caveat to that. I have the ones that I want to get there first because they’re fun. So I think the thing that I find super exciting right now is I always considered myself very much an engineer. Like I design things, I build things. That’s what I do. It’s very fun. But I think the collaborations I’ve had recently with biologists over the last five years or so and these applications for scientific discovery are incredibly fun. Like, I love those. I love interacting with these people. I love learning new things about ants and things that people have been looking at for decades or centuries even. So that’s something that I really love and I love getting the capabilities up online to help those folks. I think the most exciting in terms of application is always going to be the medical side for me. The idea that you can literally help people. In terms of both the kind of devices that we would ultimately be able to build, but also some of the sensors that we’re able to design that could help people better interface with larger skill robots for things like rehabilitation in the like,
Richard Jacobs: Well, what are some specific applications that you’re working towards?
Sarah Bergbreiter: So one application is more on this kind of interface to a human-robot interaction interface. So that is we basically designed, this is with my student Louis Stankovich, who’s down at the University of Maryland still. And basically, we designed this kind of array of capacitors, capacitive sensors that you mentioned, like the compression bands that you could put on your arm, like a sleeve basically. And so these are designed to kind of go over your forearm and with that, along with some machine learning, you can actually detect a bunch of different hand motions and grass that somebody could actually be doing. And this could be incredibly important for interfacing with a prosthetic or a rehabilitation robot or even AR VR type capabilities in the future as well. So I think that’s kind of a current project that has a lot of very near term commercial application.
Richard Jacobs: Yeah, I’ve heard once you get quote-unquote small enough, the normal forces that effects robots change and other ones become stronger than the I mean, can you talk about that a little bit? Does that happen to the scales you work at?
Sarah Bergbreiter: Yeah. So especially for the small scale robots, the mobile robots that we work on I think it’s not a question of physics changing, which also people often mistakes. So we don’t go into quantum physics or anything like that. It’s all still very common, Newtonian physics. But the physical quantities that you care about changed dramatically. So a large scale robot that’s walking or running, for example, mass is a pretty critical part of that. And you don’t really care about if the foot is a little bit stickier to the floor. Like maybe you get a slightly better grip, but you know, it’s not really imperative. It’s not going to dramatically affect the motion of your robot in comparison to what mass will. At the various scale that we work at kind of the, one milligram 10-milligram scale, mass is no longer an important force in comparison to, for example, those forces that might adhere your feet to the ground.
In fact, some of the little legged robots that we designed a couple of years ago, one of the big problems is that once you put them on a surface, you built them, you put them on a surface, they didn’t come off, they couldn’t actually move because they were stuck just from the adhesive forces with their feet and their mass was just not enough. Their inertia was not enough to get them going. And so these are just things that if you’re designing big robots, you just don’t think about. And so it just comes down to changing the kind of models that you use at these smaller scales. So things that you would just throw away as negligible at the big scale you do actually now care about at the small scale.
Richard Jacobs: So robots, when they get small enough, you literally don’t have enough mass to overcome the sticky forces?
Sarah Bergbreiter: You can if your materials system is designed that way, so that happened to us and turned out, we could basically oxidize the surface of the polymer that we were using for the legs and the feet. And add effectively a really tiny thin glass layer on the outside of that and make it a lot less sticky and then we could move just fine. So, it just comes down to what those materials systems are, but it’s something that obviously insects and our small robots depend on to be able to climb walls and grab your potato chip and that kind of thing. But we, big robots, once again, it’s just not, it doesn’t show up in the models.
Richard Jacobs: Are there any benefits that you can take advantage of it, these really small scales, any things that come into your favor?
Sarah Bergbreiter: Yeah. I mean, you can take advantage of these forces. That can be a pain in the butt as well. So, you know what I just mentioned, the idea of being able to climb, for example, if I’m really small, I can take advantage of these adhesive forces to be able to climb, for example, much better than I could. For a larger robot, much harder for larger robots, they’d have to use entirely different mechanisms to do that, whereas I might be able to get away with the same kind of mechanisms. They’re much more robust in general. So the scaling is in your favor. If you ever watch bugs fly around, they’re often just crashing into surfaces and then they’re okay. And that’s not something that we as larger organisms can do well or you know, any robots that are larger can do well. And so if I drop my little robot, you know, it’s probably fine. Whereas if I dropped my larger robot from the same height, it might be bourbon into tens of pieces.
Richard Jacobs: Okay. Cause then the low mass, lower inertia, lower momentum. So there’s less damage and they bump into stuff and fall.
Sarah Bergbreiter: Yeah. There’s less energy in general and you actually get some interesting scaling benefits just in terms of kind of beam bending and stresses and strains as well.
Richard Jacobs: Any efficiency in terms of energy use or is it the same at that scale?
Sarah Bergbreiter: They typically, so there’s a bunch of weird metrics around efficiency. So one of the biologists like to use something called cost of transport and robot cists has kind of adopted this to some degree, but it’s basically the energy that it takes to move a given mass and given distance. Sometimes people add gravity to make it dimensionless, but you can imagine energy divided by mass times distance. That metric tends to look really bad if you’re really small because energy doesn’t always scale the same way, for example. And so it can go up dramatically in terms of efficiency in actuators and kind of the things that would ultimately drive your robot. You also end up looking pretty bad. So electromagnetic motors that people use for larger robots can be pretty efficient, like 90% or so. Whereas the actuators that people typically use to drive small scale robots, like the ones that we work on more on the order of 10% at best you know, fractions of a percent at worse.
And so we tend to have a little bit of an efficiency problem with these skills, but those 10% actuators are certainly on the order of what muscles can do. Typically people say on the order of 15% for muscle. And so I think that I’m not terribly concerned about being able to have the useful autonomous operation on these small scale robots. A snickers bar sugar’s about an order of magnitude higher than what we can get for lithium polymer batteries. So if you take that into account and the kind of muscle versus motor efficiency into account, yeah, maybe you’d last 10 times or a 10th the time that an insect would last. But I can tell you that the insects set occasionally run around. My house can last quite a long time. And so I think you can still do quite useful things even autonomously in these small scales.
Richard Jacobs: Lasers, the dramatic drop in efficiency because of the type of locomotion.
Sarah Bergbreiter: So that’s a good question. Because mass scales down you tend to be able to take a little bit less advantage of storing energy in springs for example and returning that energy. But if you look at so a lot of our research, one of the things that we’ve done is actually specifically looked at legged locomotion at very small scales. And so we’ve designed these physical models, we get around the actuator problems so that we can just look at locomotion by designing very these magnetically actuated legged systems. And so in those cases, you can actually still use, you still get it quite a bit of benefit from having compliant legs and being able to use springs, those were on the order of grams down to milligrams. It definitely gets to be less of an advantage as you get smaller though.
And so we basically still need to look at new models to really understand that a little bit better. And if you run the kind of basic math, there are different locomotion methods that are better at these small scales or at in general. So running is obviously theoretically very efficient. If you can actually store all of your energy in the spring and then release that as you’re running can be theoretically up to a hundred percent efficient. Obviously, it’s not in general, but jumping, you tend to get kind of a fixed efficiency out of something like that. Flying typically is not that efficient. Things like crawling, you lose a lot, so that interaction with the ground, but that’s something you can take advantage of them. Again, those surface forces at small scales. So it’s a fairly complicated problem that nobody’s really teased apart yet. But it’s a fantastic question.
Richard Jacobs: Well, what does nature do and seem to prefer at the scales that you’re looking at? Does that include, is it has the most efficient locomotion types or no?
Sarah Bergbreiter: Yeah, I mean, nature’s always a good source to look at. And obviously, things at these scales tend to have legs. Smaller, you tend to move through different kind of mechanisms. But things typically for locomotion will walk or run at these scales. Jumping insects typically used more like an escape mechanism, although some insects will actually use that to get from place to place. And flying is obviously something that some insects are able to use as well. But once again, energetically costly to do that. But you know, we can do things in engineering that biology cannot do because of its starting point and so, and the materials and kind of muscles and such available to it. So we can come up with potentially more clever ideas in engineering as well.
Richard Jacobs: Are there any new clever locomotion types that either you’ve discovered or you’ve seen?
Sarah Bergbreiter: So, I guess one thing that we’ve done that I’d say is not at all bio-inspired, but kind of a fun way to get around when you’re small is this is work with the students who’re at the army research lab, Wayne Sherman and basically the idea was using the Nano energetics to create thrust. So we are effectively jumping around with micro rockets effectively. So you could etch silicon like silicon, the element or a silicon wafer to be Nanoporous. So it has all these very small pores, looks kind of like Swiss cheese and you coat it with an oxidizer and you add a little heat and you’re able to get a lot of energy out. So the benefit is that you know, we can store energy already in this kind of form instead of having to convert battery energy to some kind of mechanical energy. And so we can actually use this chemical energy directly, however, a jump which is cool and works reasonably well.
Richard Jacobs: Why does silicon do that when you make it chorus like that?
Sarah Bergbreiter: You’re getting out of my scope of understanding. I mean, a lot of that comes down to the chemistry, but basically, it’s the surface energy in the silicon in those silicon oxide bonds that are created.
Richard Jacobs: Okay.
Sarah Bergbreiter: You know porous is the surface area. That’s what the Nanoporous are important for.
Richard Jacobs: Right. Any types of locomotion or things that you’re working on, maybe it’s going to be a few years of where you get there, but it’ll be a big milestone for you.
Sarah Bergbreiter: Oh I mean there’s always lots of that will be a few years out. On the locomotion side, I think the really exciting bit is adding more autonomy to the locomotion. So most of what people have done at the scale is either tethered because you need that power source. We’re magnetically controlled and we’ve done both in the past. And I think that we’re basically currently working on some new actuators that I think should just be able to get us actual autonomous operation at these kinds of scales, the kind of a say 10 to 100-milligram type scale. And I’m pretty excited about that.
Richard Jacobs: How small of a camera can you be or how small of a pincer or an armor, you know, have you found the limits of some certain things that you’d want to put on these objects but you can’t?
Sarah Bergbreiter: I mean you can always do really small things if you really want to. So I mean we have people in this department who go all the way down to the DNA origami creating sensors. So you can create Nanosensors if you really want to. I think the size limits for us is often going to be the energy source. So the battery or any kind of fuel storage that you might ultimately want to use and protection that is going to be packaging that effectively are going to be some of the limits. We can make really tiny mechanisms we can make really tiny actuators. A lot of it comes down to how you interconnect everything, put all the pieces together. So we’ve been working on some new microfabrication techniques involving these kinds of microscale 3D printing options that exist now. And a lot of that is to be able to get that functionality exactly where you want it to go in those interconnections exactly where you want them to go. I mean, I can make tiny motors, I can make tiny sensors, I can make tiny microcontrollers tiny batteries, tiny mechanisms, putting them together, that’s the big challenge. And putting them together often in a very 3d way, allows me to transmit my forces in 3d to the world around me.
Richard Jacobs: But why is that a big challenge? What makes it so difficult?
Sarah Bergbreiter: So one reason that’s a big challenge is that in order to make the best microcontroller, the best actuator, the best mechanisms, they’re often done in multiple different processes. And then this question of, well, okay, I have a bunch of motors or I have a bunch of mechanisms, how do I put them all together? Like that’s really hard to do at the sky’s skills that we’re talking about. So knowing to do oftentimes with a little Legos and stuff, I have kids is like trying to get all the little pieces together. It can be challenging, like when you’re talking about things that are orders of magnitude smaller than that, much more challenging as well. And so I think that’s part of the problem. Part of the problem is just, you know, once I’ve made these things separately or I make them typically in these very 2d processes, so I would typically think of microfabrication and effectively an extruded duty process. It’s really hard to make 3d things in that process. And so that contributes to some of the challenges. And then just, you know, I had a friend at one point who said, the robotics is the study of connectors, like really hard to get all the wiring to where you want it to go. So you’re limited in the kind of actuators that you can use because you just can’t have like 15 different wires going to a leg that’s only a millimeter long. So there’s a lot of I think fun challenges in terms of actually putting all of these pieces together.
Richard Jacobs: I guess the smaller you want to make things, the smaller the machines need to be that manipulate the small things. It needs to be even smaller. The wires that connected with the things that connect them need to be even smaller than they are more subject to different effects than the little machine you’re trying to build.
Sarah Bergbreiter: Yeah. Richard Fine them gave a talk at one point, a title, there’s plenty of room at the bottom. We talked about all of these kinds of fun engineering and science challenges that very small skills, but one of the things he talked about in that talk was tiny hands building tiny hands. And so exactly the problem that you mentioned of. You know, I need small robots to build smaller robots. And there is some progress on that front. So there are a lot of folks who are looking at these small scale robots for manufacturing type things, including to make other small robots. Yeah. So there’s a lot of fun stuff to be done in that area.
Richard Jacobs: Okay. We’re good. So what’s the best way for people to find out more and get in touch with the lab or you?
Sarah Bergbreiter: Oh, probably the easiest way is to search for my name, CMU that’s named Carnegie Mellon. So Sarah Bergbreiter. Yeah, so that’s probably the best way.
Richard Jacobs: Okay. Well, very good Sarah. Thanks for coming on and sharing your knowledge. I appreciate it.
Sarah Bergbreiter: Thank you very much.
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