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Robot Designed to Grow into Shapes, Spaces

Robotic tube

Robotic tube extending through glued surfaces (Stanford University)

21 July 2017. Engineering researchers created a new type of robot that grows to extend its form into spaces like a vine, rather than move to different locations. A prototype growing robot, designed by a team from University of California in Santa Barbara and Stanford University, is described in the 19 July issue of the journal Science Robotics.

The system, known as a vinebot, is the product of the Collaborative Haptics and Robotics in Medicine lab led by mechanical engineering professor Allison Okamura. The researchers are seeking better ways for robotic devices to travel and navigate unfamiliar terrains and tight spaces while responding to both external conditions and operator controls. The team was particularly interested in alternatives to locomotion, which often requires moving parts and sometimes power supplies.

Okamura and colleagues used growing vines and nerve cells as models, which grow their length rather than move from one location to another. The team employs soft materials in a tube that extends its length through the process of eversion, or turning inside out like a pants pocket. The system is powered with air pressure, but water pressure could also be used. Onboard sensors and a camera help steer the tube, with a small bulb to light the way.

The vinebot tube, using thin inexpensive polyethylene materials, extends from a base equipped with an air compressor. A spool of material feeds the tube as it grows, controlled by a winching motor. The tube extends in segments of about 2 centimeters, with each segment controlled by an adhesive latch that remains closed. When the tube is pressurized, and the latch for the segment is at the leading tip of the tube, the latch opens allowing for the tube to extend.

The researchers used natural models such as fungi and pollen tubes for designing vinebot’s navigation. The tube has small control chambers along the sides that inflate to change the tube’s growing direction. To make a left turn, for example, the right-side control chamber inflates, lengthening that side of the tube, and moving the tip of the tube to the left. The team notes that no more air pressure or separate motors are needed to turn the tube, keeping the design simple. The tube also is able to to carry items for delivery. The researchers wrote software to control the vinebot, capturing images from the camera in the tip, with algorithms that process the images and alter the course of the tube almost instantaneously.

The team tested vinebot tubes over various challenging surfaces, including sticky surfaces like flypaper and glue, as well as nails. The nails could puncture the tube along its length, but the tube extends only from the tip, so as long as air pressure can reach the leading section, the tube continues to grow. Other tests squeezed the tube under a door about 10 percent of the tube’s diameter, and fit under and lifted a crate weighing 100 kilograms (220 lbs.).

Further tests sent the tube through the space above a dropped ceiling to demonstrate its ability to navigate around unfamiliar obstacles, while towing a cable. And in a separate demonstration, the team directed vinebot to extend up in the air to form a free-standing framework for sending out a radio signal.

This first prototype, says Okamura in a Stanford statement, is designed as much to understand the capabilities of the technology as much as build a working system. “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.”

Okamura and first author Elliot Hawkes filed a provisional patent application for the technology. In addition to public safety applications, such as search and rescue, and inspection functions, the researchers believe the technology can also be applied to medical devices. One version of the device is as small as 1.8 millimeters, with potential applications in diagnostics and drug delivery.

In the following video, Okamura, Hawkes, and colleagues tell more about the vinebot.

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