Multiplexed electrospraying of water in cone-jet mode using a UV-embossed pyramidal micronozzle film

The electrospraying of water in the cone-jet mode is difficult in practical applications owing to its low throughput and the electrical discharge caused by the high surface tension of water. A film with multiple dielectric micronozzles is essential for multiplexed electrospraying of water in cone-jet mode without electrical discharge. Thus, a pyramidal micronozzle film with five nozzles was fabricated using the UV-embossing process. The pyramidal micronozzle film consisted of pyramidal micronozzles, a micropillar array, and an in-plane extractor, which were proposed to minimize wetting and concentrate the electric field to the water meniscus at the tip of the pyramidal micronozzle. The electrospraying of water using a single pyramidal micronozzle was visualized by a high-speed camera at a flow rate of 0.15–0.50 ml/h with voltages of 0.0–2.3 kV, −1.6 kV, and −4.0 kV at the water, guide ring, and collector, respectively. Three distinct modes, the dripping, spindle, and cone-jet modes, were observed and distinguished according to the motion of the water meniscus at the nozzle tip. The steady Taylor cone and jet were observed in a voltage range of 1.3–2.0 kV in water, particularly in cone-jet mode. Multiplexed electrospraying of water in cone-jet mode at a flow rate of 1.5 ml/h was performed using a pyramidal micronozzle film, demonstrating the potential for a high-throughput electrospraying system.