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Meet the Octobot, Harvard's Fully Autonomous Soft Robot

Image: Ryan Truby, Michael Wehner, and Lori Sanders/Harvard University

Researchers based at Harvard University have developed a fully autonomous, untethered soft robot. The so-called octobot, which is described today in the journal Nature, is claimed to be the first of its kind. The bot looks like a creepy see-through spider, and it may one day cruise freely through your body diagnosing diseases.

Robots as we usually conceive of them are rigid machines. They have wires and rods and circuit boards. The humanoid robot, as the trope goes, is not far beneath the surface an arrangement of technologies that might as well be leaking oil and throwing sparks. The biology, the naturalness, is skin-deep.


This poses a serious limitation when it comes to interacting with actual biological systems, which are very soft and squishy. But making robots that are likewise soft and squishy is a deep challenge. Engineers have come up with some impressive solutions—from soft fish robots to rolling caterpillar bots—but they've all suffered under the limitation of requiring the presence of hard robotic control systems and-or power sources. They are hybrid soft robots, at best.

"In each case, these robots are either tethered to or carry rigid systems for power and control, yielding hybrid soft–rigid systems," write Robert Wood, founder of the Harvard Microrobotics Lab and the current study's lead author, and colleagues.

Generally, soft robots move and manipulate through variations in pressure. You can imagine a soft robot in whatever form as a series of tiny chambers linked by channels. When some soft appendage is called into action, a subset of chambers are pneumatically inflated, resulting in the desired motion. The set of motions and actuations that can be effected in this way is basically limitless.

That is, they are limitless within the bounds of their power source and control system. Soft robots need a pressure source, and this is where things get rigid.

Simply, the octobot packs its own pressure source. It's built in. This takes the form of a monopropellant fuel—a chemical that, when exposed to certain conditions, breaks down and releases energy very quickly in the form of hot gases.


"[Monopropellants'] rapid decomposition into gas upon exposure to a catalyst offers a strategy for powering soft robotic systems that obviates the need for batteries or external power sources," Wood and co. write.

At the heart of the octobot is a soft microfluidic circuit. Imagine a computer chip that has valves instead of logic gates. The job of this circuit is to take an inflow of monopropellant fuel and to distribute it to the correct chambers to be inflated to result in a particular motion. That motion can be seen in the video below:

That is so far the only motion. "The realization of autonomous soft robots will require the integration of different materials and functionalities, such as actuation, powering and logic," write Italian microroboticists Barbara Mazzolai and Virgilio Mattoli in a separate Nature commentary. "The octobot represents the minimal system that demonstrates the potential of this approach."

In other words, it's a proof of concept. But still, it's also a seed for the imagination. In addition to healthcare applications, we can imagine soft robots squishing their way through search and rescue operations, exploration missions, and myriad industrial applications in which danger and the need for soft appendages intersect. The Harvard octobot isn't itself likely to be very useful for those applications, but we can now imagine a future octobot featuring more complicated circuits performing more complicated and thus more practical tasks.