Alejandro Cortese, Ph.D. ’19 displays a silicon-on-insulator wafer that contains finished CMOS “brains.” (Image:

Cornell University engineers have installed electronic “brains” — smaller than an ant’s head — on solar-powered robots so that the machines can walk autonomously, sans external control.

Many have previously developed microscopic machines that can crawl, swim, walk, and fold themselves up, but there were always strings attached — literally — to generate motion.

“Before, we literally had to manipulate these strings in order to get any kind of response from the robot,” said Itai Cohen, Professor of Physics in Cornell’s College of Arts and Sciences. “But now that we have these brains on board, it’s like taking the strings off the marionette. It’s like when Pinocchio gains consciousness.”

The development sets the stage for a new breed of microscopic devices that can track bacteria, sniff out chemicals, destroy pollutants, conduct microsurgery, and rid arteries of plaque.

The “brain” in the new robots is a complementary metal-oxide-semiconductor (CMOS) clock circuit that boasts 1,000 transistors, as well as an array of diodes, resistors, and capacitors. The CMOS circuit generates a signal that produces a series of phase-shifted square wave frequencies that then set the gait of the robot. The robot’s legs are platinum-based actuators; both the circuit and the legs are powered by photovoltaics.

“Eventually, the ability to communicate a command will allow us to give the robot instructions, and the internal brain will figure out how to carry them out,” Cohen said. “Then we’re having a conversation with the robot. The robot might tell us something about its environment, and then we might react by telling it, ‘OK, go over there and try to suss out what’s happening.’”

Itai Cohen, Professor of Physics, compares the innovation of installing CMOS circuits on microrobots with the moment "when Pinocchio gains consciousness.”

The new robots are approximately 10,000 times smaller than macroscale robots that feature onboard CMOS electronics and can walk at speeds faster than 10 micrometers per second.

“What this lets you imagine is really complex, highly functional microscopic robots that have a high degree of programmability, integrated with not only actuators, but also sensors,” said Dr. Michael Reynolds, Postdoctoral Researcher in Cornell’s College of Engineering. “We’re excited about the applications in medicine — something that could move around in tissue and identify good cells and kill bad cells — and in environmental remediation, like if you had a robot that knew how to break down pollutants or sense a dangerous chemical and get rid of it.”

Here is a Tech Briefs interview (edited for clarity) with Reynolds.

Tech Briefs: What’s the next step in your research?

Reynolds: We’re working on a few next steps. We’re currently building robots with onboard optical and chemical sensors to allow them to follow light or search out chemical sources. We are also building new legs for these robots to allow them to move through tissue or other complex viscoelastic environments or to walk on land instead or in addition to underwater. And we are working on microscopic robot swarms with robots that interact with each other as well as their environment.

Tech Briefs: When will this technology be commercially available?

Reynolds: We think we are still years away from microscopic robots like the ones we describe here being commercially available. The advance we report here — getting integrating microscopic robots with CMOS electronics — is a big one. But it will take achieving some of the next steps described above and then testing those robots in real-world environments before they are a commercial product. We are particularly excited about applications in medicine, which requires a lot of testing before the robots could be used in clinical settings.

Tech Briefs: Will there be a large market for it? Will it catch on?

Reynolds: We hope so! Ultimately, I think there are a large number of diverse applications for autonomous microscopic robots from distributed sensing/IoT applications to breaking down pollutants in the environment to building highly adaptable structures from microrobot building blocks. In the near term, however, we are focusing on medical applications in particular, especially ones where you can closely monitor and direct the robot. We think this is a promising first direction since being small and minimally invasive is a big advantage in medical applications.

Tech Briefs: How will this further the robot sector and advance research?

Reynolds: When you imagine a robot — whether a sci-fi robot or robots for industrial assembly — you typically imagine something that couples mechanical motion and electronic control and sensing. But that motif for a robot did not exist at the micro-scale before the work we are doing. So, this work advances the robot sector by taking the same parts and pieces that usually make up a robot and shrinking them down to the micron scale.

Regarding advancing research, we think these robots will make it possible to study things you couldn’t before. For instance, there’s a lot of interest in studying and controlling the behavior of swarms of microscopic robots, but there is typically a big trade-off between the complexity of the individual robots and the number of robots in your swarm. Since these robots are so small, you could pattern hundreds of thousands of them on a single eight-inch wafer. And since they have onboard electronics, you could program them to interact with each other and their environment, and even program some to behave one way and some to behave another.

Tech Briefs: Are you working on other such advances?

Reynolds: Yes, I've noted a couple of the other things we’re working on — robots with sensors, robots that move in different environments, etc. — but I’ll mention one more. We also recently had a paper come out where we demonstrated that these same actuators could be wired to electronics on chips and used as artificial cilia. In that case, you can design your actuators and circuits, and program the flow of fluids at the micron-scale. Overall, we’re really excited about marrying microactuators to microelectronics — there are a lot of promising directions to go in and we are really just starting to explore them.