It’s a game a lot of us played as children—and maybe even later in life: unspooling measuring tape to see how far it would extend before bending. But to engineers at the University of California San Diego, this game was an inspiration, suggesting that measuring tape could become a great material for a robotic gripper.
The grippers would be a particularly good fit for agricultural applications, as their extremities are soft enough to grab fragile fruits and vegetables, the researchers wrote. The devices are also low-cost and safe around humans.
The team published their process and design in the journal Science Advances. They call their robot GRIP-tape, with GRIP serving as an acronym for Grasping and Rolling In-Plane.
Building the ideal robotic gripper is still a work in progress. Existing grippers that can expand are bulky because they need additional mechanisms to get gripping appendages to expand. The gripper the UC San Diego team developed solves this problem.
That’s because the tape is both robust and flexible; can be stored in a small container when retracted; and can reach far when extended. After a series of trial-and-error experiments, the engineers determined that the best configuration for a gripper is actually two of the tapes bound together with adhesive.
“We like to look for non-traditional, non-intuitive robot mechanisms. The tape measure is such a wonderful structure because of its combined softness and stiffness together,” said Nick Gravish, the paper’s senior author and a faculty member in the UC San Diego Department of Mechanical and Aerospace Engineering.
The gripper has two “fingers,” made of two spools–each made of two rolls of measuring tape bound together. Each spool is rolled up in a compact configuration, with only a small part extending out in a triangle shape to form a finger. These triangle sections are controlled by four motors that each control the finger’s motion.
Each finger can move independently. The triangle sections can lengthen to reach objects that are farther away. They can also retract to bring objects closer to the robot arm the gripper is mounted on.
The researchers had already worked with measuring tape as part of a grant from the National Science Foundation to investigate soft materials that could bend while holding their shape.
Measuring tape is springy—you can bend it any way you want and it goes back to its original state. It’s also made of steel, which is both robust and durable, as well as thin enough that it won’t damage objects on contact. In fact, it’s as soft as the silicon used in most soft robots.
The gripper is unique because it uses the whole length of the tape as a gripping surface. The tape can also move to rotate objects or act as a conveyor belt. The gripper can hold a wide range of objects with different shapes and stiffness, from a rubber ball or a single tomato to a whole tomato vine or a lemon. Because the tape itself can act as a conveyor belt, the gripper can then deposit the objects it grasps into containers.
Because the tape is flexible, it can also navigate the obstacles the gripper might encounter on the way to picking up an object.
Experiments showed that the gripper could easily lift large fruits like fresh lemons.
Next versions of the gripper could improve on the original by adding advanced sensors and AI-driven data analysis so that the gripper can operate autonomously.
More information:
Gengzhi He et al, Grasping and Rolling In-plane Manipulation Using Deployable Tape spring Appendages, Science Advances (2025). DOI: 10.1126/sciadv.adt5905. www.science.org/doi/10.1126/sciadv.adt5905
University of California – San Diego
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A new robotic gripper made of measuring tape is sizing up fruit and veggie picking (2025, April 9)
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