If you compress a plate with accordion-like cells, a kink wave runs through it, like a wrinkle in a rug when you push it with your foot. Such waves can switch the material between two stable shapes, and this is the basis of mechanical memory. But if a table leg gets in the way of the wrinkle, it gets stuck. In a new study, researchers showed how to nudge it loose without brute force.

The stuck kink has its own natural frequency, which falls into a band gap — a range where sound does not propagate in the material. If you send two sound waves with close frequencies from the edges, their beating (slow swelling and fading) exactly matches this natural frequency. Energy is pumped into the kink, it rocks back and forth, and jumps over the defect.

This method does not require local actuators or large deformations. You just attach a pair of vibrators to the material and tune their frequencies. This opens the way to scalable mechanical memory: cells can be switched by sound without touching each one individually. And such memory is not afraid of impacts or dust — unlike electronics.