Mechanistic insights into ultrasonic vibration-induced avoidance behavior of fouling organisms on Ti alloy surfaces.

Ultrasonic marine antifouling technology has attracted considerable attention due to its strong potential to mitigate biofouling on Ti alloy marine equipment. However, existing studies have largely focused on acoustic field effects within the surrounding water, while a mechanistic understanding of how ultrasonic vibration influences the biological adhesion process at solid-liquid interfaces remains insufficient. In the present study, the interfacial avoidance mechanisms induced by ultrasonic vibration against representative marine fouling organisms, including barnacle larvae and Platymonas, were systematically investigated. The results indicated that ultrasonic vibration induced dynamic instability at the Ti alloy/seawater interface and generated periodic acoustic fields, which acted synergistically to disrupt the settlement and attachment of fouling organisms. Critical antifouling sound-intensity thresholds and an "energy-efficiency" balance threshold were identified for ultrasonic frequencies of 20 and 40 kHz. Based on these findings, a dual-frequency synergistic and intermittent operation strategy suitable for practical marine conditions was proposed. By matching ultrasonic actuation intervals with key biological adhesion windows, efficient antifouling performance at reduced energy consumption was achieved. An optimal cycle consisting of 20 s operation followed by intervals of 5-10 min resulted in near-complete antifouling efficiency under laboratory conditions. Furthermore, a field-deployable marine testing platform was established, and shallow-sea immersion panel tests verified the pronounced suppression of biofouling under this strategy. These results offer direct guidance for the optimization of parameters and the integration of ultrasonic antifouling systems in marine engineering. This guidance supports the practical application of coating-free, environmentally benign, and durable ultrasonic antifouling solutions.