Intelligent Machines

Meet the World’s First Completely Soft Robot

Researchers use an ingenious design to make a soft robot that moves on its own.

The “octobot” is a squishy little robot that fits in the palm of your hand and looks like something in a goody bag from a child’s birthday party. But despite its quirky name and diminutive size, this bot represents an astonishing advance in robotics.

According to the Harvard researchers who created it, it’s the first soft robot that is completely self-contained. It has no hard electronic components—no batteries or computer chips—and moves without being tethered to a computer.

The octobot is basically a pneumatic tube with a very cute exterior. To make it move, hydrogen peroxide—much more concentrated than the kind in your medicine cabinet—is pumped into two reservoirs inside the middle of the octobot’s body. Pressure pushes the liquid through tubes inside the body, where it eventually hits a line of platinum, catalyzing a reaction that produces a gas. From there, the gas expands and moves through a tiny chip known as a microfluidic controller. It alternately directs the gas down one half of the octobot’s tentacles at a time.

The alternating release of gas is what makes the bot do what looks like a little dance, wiggling its tentacles up and down and moving around in the process. The octobot can move for about eight minutes on one milliliter of fuel.

So how do you even build something like this? “You have to make all the parts yourself,” says Ryan Truby, a graduate student in Jennifer Lewis’s lab at Harvard, where the materials half of this research is taking place. The mold for the octopus shape and the microfluidic chip were among the things developed nearby in Robert Woods’s lab.   

The octobot is made out of materials that most microfluidics labs have on hand. But it took the researchers 300 tries to get the recipe right. First they place a microfluidic chip in an empty, custom-made octopus mold. Then they pour a silicone mixture into the mold, covering the chip. After they use a 3-D printer to inject lines of ink into the silicone, they bake it for four days. This seals the shape of the octobot and makes one of the inks evaporate, leaving behind hollow vessels through which the pressurized gas will flow.

Still missing are sensing and programming abilities that would afford more control over the robot’s movement. But the octobot is purposefully minimalist, meant just to show that such a soft robot can be made at all.

A researcher measures a silicone mixture that will form the body of the octobot.
A platinum ink is prepped for extrusion through a 3-D printer.
Molds like this are used to form the robot’s distinctive shape.
At the center of the octobot is a soft microfluidic chip, which acts as the bot’s “brain,” directing the motion of all eight tentacles.
The first step in assembly is pouring the silicone mixture into the mold.
Next, a 3-D printer squeezes out lines of ink, which will be suspended in the silicone body. The platinum ink will help turn liquid hydrogen peroxide into gas to move the tentacles; another ink will pave the way for vessels throughout the bot that the gas will travel through.
The full array of tools and molds the researchers use to create these bots. It took 300 tries to get the octobot to work.
A close-up of the microfluidic chip that goes inside the bot.
The mill used to create the octobot mold.
The octobot is usually colorless. Flashy dyes are sometimes added for illustrative purposes.
The colors here show the alternating routes that the gas can take through the bot, moving half of the tentacles at a time and helping it wiggle. The bot is about two inches long.
Just for fun, the ink can glow under a black light.