Deposition and splashing characteristics of ionic liquid nanodroplet impacting surfaces in electrospray

Nanodroplet collisions with solid surfaces can occur in various applications of electrospray technology. In electrospray propulsion, the deposition and splashing of droplets from the beam onto surfaces are critical to the performance and lifetime of the electrospray thrusters, but little is known about the underlying mechanisms. Therefore, this paper developed a detailed molecular dynamics model to simulate the collisions of an ionic liquid nanodroplet under varying electric fields and charges. The results show that under a 1000 V acceleration voltage, the droplet dissociates into cations and anions after a high-speed collision with the surface. The deposition characteristics are influenced by the oscillation between cations and anions and the applied electric field. When the electric field strength is low, the oscillation between ions leads to easier deposition of cations, causing neutral droplets to deposit a small amount of positive charge after the collision. Only negatively charged droplets may deposit a neutral or negative charge. When the electric field strength is high, it separates the cations and anions, resulting in significant charge deposition due to the imbalance of ion quantities on the surface. Furthermore, as the charge of the droplet increases, the deposition rate fluctuates, which is related to the momentum exchange caused by the oscillation between ions. This paper reveals the collision mechanism of ionic liquid nanodroplets in an electrospray environment, which may contribute to the further development of droplet–wall collision models in electrospray propulsion or deposition.