Cicada rib-inspired tough films through nanoconfined crystallization for use in acoustic transducers.

Acoustic transducers require films that demonstrate both toughness and fatigue resistance, presenting notable challenges when achieved through conventional nanoscale reinforcing strategies. Here, we found that the rib structure of a cicada's tymbal exhibits exceptional toughness and fatigue resistance, attributed to its unique architecture composed of alternating soft and stiff polymer layers. Inspired by this rib structure, we developed a robust artificial rib film (ARF) using a nanoconfined crystallization strategy that involves the deposition of soft polyethylene oxide and stiff phenol formaldehyde. The ARF demonstrates a toughness amplification factor twice that of the cicada's tymbal rib and exhibits an exceptionally long fatigue life. The nanoconfined crystallization restricts molecular motion and disperses external forces within the crystalline structure, thereby enhancing its mechanical properties. These improvements enable the ARF to outperform commercial polymer films as an acoustic transducer, achieving 2.7 times increase in frequency response and 2.2 times increase in displacement amplitude.