Acoustic "re-charging" of nanofiber air filters

The long-term performance of electrostatic fibrous filters is inherently limited by charge dissipation. Conventional regeneration strategies often rely on mechanical contact, which risks material damage due to localized stress. Here, we present a non-contact acoustic approach that effectively rejuvenates both electrostatic charge and filtration performance in nanofiber filters. Using electrospun poly(vinylidene fluoride) (PVDF)-polysulfone (PSF) membranes, we first removed the embedded charges, which reduced the PM_0.3 filtration efficiency to ∼75% (solid) and ∼74% (oil), with a pressure drop of 96 Pa. Subsequent acoustic stimulation (100 Hz, 110 dB, 10 min) restored the efficiency to 99.99% for solid and 92.90% for oily particles, while lowering the pressure drop to 45 Pa, performance that matches that of the pristine, as-spun membranes. This recovery stems from sound-induced fiber vibration, which activates a synergistic piezoelectric-triboelectric mechanism within the microphase-separated composite, replenishing surface charge and expanding the pore structure. The process is repeatable over 30 cycles without decay and also enhances back-pulse cleaning. By introducing acoustic energy as a distinct, non-contact regeneration regime, this work provides a scalable pathway toward energy-efficient, durable, and high-performance air filtration systems.