May 8, 2023

Dr. Carmel Majidi runs Carnegie Mellon University’s Soft Machines Lab. As director of Carnegie Mellon University’s Soft Machines Lab, Dr. Carmel Majidi leads a 15-member engineering research team that routinely makes world-changing discoveries in so-called soft robotics , a field that designs machines and robots to be more compatible with humans. He strongly believes that who does the discovery is as important as what’s discovered. “One of the driving forces behind soft robotics is the democratization of robotics, how robot design and manufacturing can be made more accessible to everyone and be something we can all participate in,” Majidi says. “That’s a lot of what soft robotics is about — not to compete with or replace more advanced systems that already exist, but to broaden the scope of what we think of as robotics and what we think of as materials and building blocks of robotic systems. Everybody can contribute and help come up with new ideas and new designs.” Majidi, 42, is the Clarence H. Adamson Professor of Mechanical Engineering at CMU and holds a B.S. degree in Civil & Environmental Engineering from Cornell University and M.S. and Ph.D. degrees in Electrical Engineering & Computer Sciences from the University of California, Berkeley. He spent four years as a postdoctoral fellow at Princeton University and Harvard University before joining the CMU faculty in 2011. Internationally recognized as a soft robotics innovator, his research has resulted in more than 80 peer-reviewed technical publications and six patents. The Soft Machines Lab garnered global attention in 2017 with its invention of Thubber , a thermally-conductive rubber material that was a breakthrough in allowing machines and electronics to be soft and stretchable. This past January, Majidi’s team created a millimeter-sized robot that can not only change shape but alternately assume a liquid or solid form and stretch, move, melt and reform itself, à la the villainous T-1000 robot from the “Terminator 2” movie. Majidi notes that a number of the lab’s breakthroughs are drawn from characteristics observed in nature: a stingray-inspired “skin sticker” that employs brain signal processing sensors; an untethered underwater robot mimicking the brittle star , a type of starfish; a repair robot derived from the motion of sea cucumbers ; a bonding adhesive that enhances robot hand dexterity inspired by the foot hairs of a gecko lizard . He recently shared his thoughts with NEXTpittsburgh on what soft robotics may look like in our everyday world right around the corner. CMU doctoral student Nolen Keeps shows a micromagnetic device embedded in artificial skin. * * * NEXTpittsburgh: When you were a youngster, did you imagine yourself growing up to invent things that might change the world? Majidi: I was driven not so much by wanting to tinker and invent things but by wanting to understand how things work. Like a lot of kids, I was really into LEGOs, and my favorite game was “SimCity.” It led me into wanting to major in engineering. What I didn’t know as a kid, but learned in college, was the crossover between our built environment and underlying principles of physics and mechanics in the natural world. Principles that apply not just to machines but to natural organisms — humans, animals, even insects — and how those organisms use mechanics and natural machinery to do extraordinary things. That’s what kept me inspired along the way. NEXTpittsburgh: How did you get involved in soft robotics? Carmel Majidi: It was during my undergraduate studies at Cornell, and it was from the perspective of biomechanics and human and animal locomotion. One of my core civil engineering classes looked at the mechanics of moving objects. The teacher saw I was very curious and asked if I would join his research lab for the summer, which looked at humans and animals as a kind of machine and then drew insights into how humans and animals move. These were insights we used in coming up with designs and guidelines to inform the design of robots. Ever since, the idea of biologically-inspired robot design has been the theme of my work. NEXTpittsburgh: To the day Thubber is invented! Majidi: That was a term our media relations person at CMU came up with, and it’s a brilliant way to capture the concept. Thubber is a thermally-conductive rubber. It’s made of a silicone rubber embedded with microscopic droplets of a special kind of metal alloy that is liquid at room temperature. We call these “liquid metals” — a special alloy of gallium and indium. By themselves, gallium and indium are solid at room temperature, but when you blend them together as a mixture, it forms a eutectic, a liquid. When the alloy is infused into the rubber, it allows the rubber to have thermal conductivity. But because the metal is liquid at room temperature, it doesn’t interfere with the rubberiness and elasticity of the silicone. It’s the best of both worlds. You have thermal conductivities that approach what you get with metals, but you have the same kind of compliance and softness, the stretchable and elastic properties of silicone. CMU doctoral student Richard Desatnik shows a soft robotics design that can keep working if parts of it are damaged or broken off. NEXTpittsburgh: Were you looking for this intentionally? Majidi: I’d been working for several years fusing rubber and liquid metal to get stretchable circuits. It was something we hit upon because we were interested in making robot skin that was soft and rubbery and could mimic skin and nervous tissue of natural organisms. We found that liquid metals were a really powerful way to incorporate electronic functionality and sensing capabilities within these soft, rubbery skins. NEXTpittsburgh: Besides the potential use for robot skin and human implants, Thubber has everyday applications for our smartphones? Majidi: A lot of applications are useful for computing. Everybody’s experienced their laptop or phone overheating when the CPU is running in overdrive trying to perform a lot of operations with all the transistors. All the heat that’s generated can’t be removed fast enough. The point of Thubber is to create a thermal interface that conforms to the features and components in your device but is thermally-conductive and helps heat dissipate quickly. Thubber can be used to manage heat in any computing device, and it’s an application where we’re finding a lot of use. NEXTpittsburgh: How does the lab come up with new ideas? Do you start with a goal, something you want to exist, and then reverse-engineer? Majidi: A lot of our discoveries begin with a very different goal than from how they end up being used. As a doctoral student, I wanted to build wall-climbing robots. The biggest challenge turned out to be the adhesives. What gets the robot to stick to vertical surfaces? We identified the gecko as a source of inspiration. It has extraordinary abilities to climb and move along ceilings. Even though my interests were initially on the engineering and control of this robot, what I ended up spending my research on was the gecko-inspired adhesive. I studied natural gecko adhesion with biologists. That was a pivot. It wasn’t my goal starting out, but one thing led to another, and I ended up doing a deep dive into a whole other area. It turned out to be useful for a lot of applications that had nothing to do with robotics. A soft robotics model using a synthetic technology designed to replicate the muscle movement of a starfish. NEXTpittsburgh: This year, the Soft Machines Lab created a miniature, shape-shifting robot that can liquefy itself and reform. This is certainly the stuff of science fiction happening now! Majidi: The team made two tiny robots that could carry and solder a small light bulb onto a circuit board. When they reached their target, the robots simply melted over the light bulb’s edges to fuse it to the board. Electricity could then run through their liquid metal bodies and light the light bulb. NEXTpittsburgh: That was inspired by insect behavior? Majidi: There is a lot of interesting crossover about looking at fire ants or swarms of insects or other natural organisms and how they behave collectively as one body or entity. That’s been an inspiration to a lot of us in engineering, and you can draw that analogy with the types of material my colleagues in China have developed. You have this ensemble of little magnetic particles and if you think of each particle as a fire ant, they have the capability of mobility. They can move individually on their own, but they can also move and work in a coordinated manner. Then you have this low melting point metal that encases all of them, and at one stage the metal could be solid and the particles are frozen together and move as one group … or the metal could be liquid, in which case the particles can move more independently. NEXTpittsburgh: You’ve often spoken of soft robotics as not just an academic discipline but as a community and a movement. Majidi: I think it’s why soft robotics has attracted as much attention as it has. If it was something only a few highly resourced labs could do at just a few different universities or companies throughout the world, it would never have been as successful as it’s been as a new engineering field. It’s really important that we have a broad spectrum of people with diverse backgrounds contributing to these fields, along with people involved and engaged as creators and adopters of these technologies. Otherwise, this will be a field that begins and ends in the lab. An example of synthetic sensory equipment. NEXTpittsburgh: We’ve been hearing for a long time from scientists like Ray Kurzweil about the concept of the Singularity , a date in the near future when the human body and brain would merge with technology and artificial intelligence. How close are we to the time when the abilities of a computer overtake the abilities of the human brain? Majidi: We’re always being overtaken by technology and by our own capabilities and our own products. Singularity relates specifically to AI or robotics or computing, but there are so many other domains in which other human products have exceeded our own capabilities. Through all the disruptive technological changes society has undergone, we’ve always managed to maintain our purpose as humans. With every stage, we’ve been able to find a new purpose. Look at the progress in artistic expression, our value systems, our religion. Our culture often coincides with these changes. With whatever form the Singularity takes, it will probably be a re-examining of what our purpose as a human is, but we’re going to come up with something after that that’s going to be a value system that makes sense of the circumstances of that age. And it will build in a logical way on past value systems. NEXTpittsburgh: What advice would you offer for anyone who wants to pursue new applications of robotics? Majidi: I tell my students not to get too fixated on the end goal. Value the discovery process and be receptive and open to letting the research itself guide you. Often it can take you in very different, unexpected directions. Sometimes that’s how the best discoveries are made. Having that kind of flexibility is a very important skill to have.