Dancing Electrohydrodynamic Tip Streaming Modulated by Faraday Instability.

Tip streaming enables flow transitions from the millimeter scale to the microscale and even nanoscale, generating tiny droplets with broad applications in precision 3D printing, nanomaterial fabrication, and drug delivery. In these applications, high-frequency jetting is required to improve efficiency. However, understanding and controlling high-frequency tip streaming remain challenging. Here, a series of dancing electrohydrodynamic (EHD) tip streaming phenomena is reported, characterized by subharmonic ejection modes under high-frequency electric fields. The underlying mechanism of this intriguing phenomenon is elucidated, which stems from global meniscus oscillations induced by Faraday instability, followed by jetting at the Faraday wave crests due to local interfacial instability. The optimal excitation frequencies of these ejections are governed by the natural frequencies of Faraday instability, while a maximum electric Bond number comparing electric and capillary effects determines the ejection voltage threshold, thus enabling precise control of high-frequency EHD tip streaming. Owing to the high excitation frequency and multi-directional jetting feature, the dancing EHD tip streaming demonstrates enhanced throughput and multi-path delivery, opening new and exciting prospects for various drop-on-demand technologies.