A joint team from POSTECH (Pohang University of Science and Technology) and Jeonbuk National University has shown that mechanical waves can be fully trapped inside a single solid resonator. Many researchers thought this was "theoretically impossible" in compact systems. The work was published on April 3 in Physical Review Letters and focuses on bound states in the continuum, or BIC, where waves stay trapped and do not lose energy, even though, in a continuum, there are paths for them to escape.