Multi-frequency wave focusing in rationally pruned disordered networks

The spatial structure of metamaterials can be designed to focus deformations or waves at a specific location. However, input control of this behavior, allowing for focusing waves at multiple targeted locations, remains challenging. Here, we exploit frequency as a control parameter and show that frequency-controlled wave focusing can be realized by rationally pruning random elastic networks. Our approach is robust, and we also demonstrate such wave focusing experimentally. Our study revises the concept of wave focusing and opens up a viable route for the design of new generations of acoustic sensors, energy harvesters, lenses, and programmable acoustic media, free from the limitations imposed by periodicity.