This 3cm super soft silicone tube has a string inside, attached to the end. When the string is pulled 1cm you get multiple curls. Interestingly, the tube takes a very different path on the way back when the string is released!
Tentacles and tendrils are a focus of biomimetic soft robotics, taking inspiration from structures like the cucumber tendril. This one uses a string as a mechanism, but tendrils are more commonly controlled by inflating with air, or bringing them into contact with a chemical that swells part of the structure. Recently, an air-filled micro tendril was able to lasso an ant without harming it.
The thread in the video was slurped in to the soft tube using vacuum. Automated methods to insert strings and wires in 3D printed polymer parts would make a lot of simple, yet interesting soft mechanisms possible.