Stanford University Creates Soft Robot That Grows Like a Vine

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[Image: L.A. Cicero]

Stanford University is home to some of the most advanced research and respected scientists in the world, and what’s especially impressive about the work coming out of the university is that much of it has been accomplished with only the simplest of tools and materials. Earlier this year, Stanford researchers came up with an effective way to diagnose malaria using a 3D printed version of a child’s toy; now, another research team from the university has created a fascinating robotic tool that’s basically just a plastic tube.

The newly developed robot looks something like a long balloon, but it’s much more resilient – and useful. The researchers were inspired by things in nature that grow to vast lengths across distances, such as fungi, vines and nerve cells. In a paper entitled “A soft robot that navigates its environment through growth,” which you can access here, the researchers describe how they created a robot from a soft, flexible plastic material that was folded inside of itself. You may have played with a toy that uses a similar concept; I used to see them all the time, those slippery tubes that you could never get a grip on because every time you tried to grab one, it would turn inside out and slide right through your hands.

The robot, on the other hand, rather than turning inside out and right side in again and again, unfolds or “grows” when pressurized air is pumped into one end. Watching it is like seeing a time-lapse video of a vine growing, and it doesn’t resemble a robot at all, at least not a robot as they’re typically visualized.

“Essentially, we’re trying to understand the fundamentals of this new approach to getting mobility or movement out of a mechanism. It’s very, very different from the way that animals or people get around the world,” said Allison Okamura, professor of mechanical engineering and senior author of the paper.

The Stanford team has also considered alternate versions of the robot in which the pressurized air would be replaced with fluid, but the concept is the same. What makes it work so well is the fact that as the tube lengthens, only the growing end of it is actually moving; the rest of it remains in one place.

“The body lengthens as the material extends from the end but the rest of the body doesn’t move. The body can be stuck to the environment or jammed between rocks, but that doesn’t stop the robot because the tip can continue to progress as new material is added to the end,” said the paper’s lead author, Elliot Hawkes, a visiting assistant professor from the University of California, Santa Barbara.

The researchers tested the robot by having it “grow” over sticky surfaces like flypaper and glue, as well as nails that punctured it but didn’t cause any problems because, since the tube remained in place, the nails also stayed in place and acted as plugs to fill the holes they had made. The robot then grew up an ice wall to deliver a sensor that could possibly be used in real-world applications to detect carbon dioxide produced by people trapped in a collapsed building, for example. The robot also snaked beneath a 100-kg crate, lifting it as it moved beneath, pushed its way under a door and grew up into the air like a plant.

Graduate students Joseph Greer, left and Laura Blumenschein, right work with Elliot Hawkes, a visiting assistant prof. from UCSB, on a prototype of the vinebot. [Image: L.A. Cicero]

In one particularly intriguing experiment, the robot traveled through the space above a dropped ceiling, proving its ability to navigate through unknown spaces. It also pulled a cable through its body while above the ceiling, offering a potential new way to route wires through tight spaces.

“The applications we’re focusing on are those where the robot moves through a difficult environment, where the features are unpredictable and there are unknown spaces. If you can put a robot in these environments and it’s unaffected by the obstacles while it’s moving, you don’t need to worry about it getting damaged or stuck as it explores,” said Laura Blumenschein, a graduate student in the Okamura lab and co-author of the paper.

A system of latches, set up in a continuous row within each control chamber, open to allow for the lengthening function; it is in this system that 3D printing may come into play for larger production of these robots. The paper describes the latch system:

“Within each control chamber is a continuous row of latches, with each latch roughly 2 cm long (body diameter is 3.8 cm). Each engaged latch crosses pinched wall material; in this way, the side lengthens when the latch is opened without requiring the material to stretch… The opening of the latches is controlled by the pressure in its control chamber as well as the location of the latch. When a control chamber is not pressurized, the pressure from the main chamber keeps the latches closed. However, when the control chamber is pressurized, a latch can open, but only if it is at the tip of the robot body. When at the tip, the curvature causes the latch to release and the section to lengthen. In contrast, if the latch is on a straight section, it remains closed because of the interlocking of the latch. The latches are manufactured from a combination of sheet steel and polypropylene and attached to the outer wall using a soft viscoelastic adhesive (TrueTape LLC). The latches can also be produced by 3D printing for large-batch fabrication. The latches can be reset after lengthening for a reusable system.”

The team is also looking at different, tougher materials such as nylon and Kevlar, as well as robots that could be manufactured automatically instead of by hand – there’s always a possibility of 3D printing becoming more involved in the future. The researchers have also created a 1.8 mm version of the robot, and believe that tiny versions could be used as medical equipment, instead of tubes that are pushed through the body.

Authors of the paper include Elliot W. Hawkes, Laura H. Blumenschein, Joseph D. Greer and Allison M. Okamura. You can learn more about the soft robot below:

Discuss in the Stanford forum at

[Source: Stanford University]


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