Physicists may have found a solution for the rage-inducing tangles that crop up in everything from electronics cords to necklaces: to free a single thread from a tangle of many, you must shake it not too fast and not too slow but with just the right frequency.
Ishant Tiwari at the Georgia Institute of Technology in Atlanta and his colleagues created a vibrating robot to determine how to best jiggle a single thread from such a tangle.
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The researchers gathered cotton fibres into balls by rolling them around in a box. This ensured that all the tangles they tested would be similar. The tangles were each attached to a piston on a robot by a single thread.
Tiwari and his colleagues set the robot to jerk up and down at various frequencies and vibrate the tangle, which revealed that there is a sweet spot for the perfect untangling frequency.
The robot identified an ideal shaking frequency of 17 hertz (shown in the middle)
Ishant Tiwari, Bhamla Lab
When the shaking frequency was low – just a few shakes each second, or a few hertz – the thread that was attached to the piston moved together with the tangle and it stayed stuck. At the high end, greater than around 37 shakes per second, the tangle also remained jumbled. The energy of the shaking was diverted into damped oscillations across the whole tangle, so it tugged less on the specific thread they were trying to release from the ball.
But at about 17 shakes per second, the tangle jumped and jerked more chaotically, and each twitch contributed a small pull on the thread. When the effect of these pulls accumulated, the thread came loose from the tangle.
The researchers have presented results on only one type of thread so far, but their work may help unravel a more general property of the fibre tangles that pervade our daily lives – and how to deal with them.
