A novel dancing electrospray phenomenon is reported characterized by high-frequency, robust, and multi-directional alternating ejection modes. This phenomenon arises from the electrohydrodynamic (EHD) tip streaming at the crests of Faraday waves excited on the liquid meniscus, and it offers significant advantages in high-throughput and multi-path delivery for applications such as EHD printing and electrospinning.
Abstract
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. It is shown that the optimal excitation frequencies of these ejections are governed by the natural frequencies of Faraday instability, and introduce a maximum electric Bond number comparing electric and capillary effects to determine 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.
Advanced Science, EarlyView. Read More
