To the annoyance of parents everywhere, children love playing with tape measures. They will lock the extended tape in place and notice how a slight curve keeps the metal strip rigid. Then they will release the lock and delight in how a spring retracts the tape with a satisfying thwack.
Roboticists at the University of California, Los Angeles have been playing with tape measures, too. They have discovered that the rigid but bendy tape can be used as a new type of limb that acts something like a spider monkey’s arm or an octopus’s tentacle.
The limb is extremely simple. A metal tape rolls through a hooked end piece and returns to a spool at the base. The spool can either let out more tape to extend the limb or pull the tape in to retract it. By hooking the end piece over a branch or pipe, the arm can pull the robot up. In tests, the system can climb shelves or ladders at 1.5 body lengths per second.
“The final goal envisioned for this project is a three- or four-limbed robot capable of moving freely in 3D space using its extendable limbs,” wrote Justin Quan and Dennis Hong in their paper, “Flexible Long-Reach Robotic Limbs Using Tape Springs for Mobility and Manipulation,” published in the June 2023 issue of Journal of Mechanisms and Robotics. In time, robots sporting this system could shoot out and retract limbs to travel anywhere these arms can reach.
