Drop-on-demand satellite-free drop formation for precision fluid delivery. (31st August 2018)

• Record Type: Journal Article
• Authors: Yang, Lisong; Kapur, Nik; Wang, Yiwei; Fiesser, Fritz; Bierbrauer, Frank; Wilson, Mark C.T.; Sabey, Tim; Bain, Colin D.
• Is Part Of: Chemical engineering science. Volume 186(2018)
• Page Start: 102
• Page End: 115
• Publication Date: 2018-08-31
• Subjects: Drop-on-demand -- Satellite -- Flow rate -- Newtonian and Non-Newtonian fluid -- Digital printing; Chemical engineering -- Periodicals; Génie chimique -- Périodiques; Chemical engineering; Periodicals; Electronic journals; 660
• DOI: 10.1016/j.ces.2018.04.014
• Languages: English
• ISSNs: 0009-2509

Abstract

Highlights: Analysis of a liquid dispensing system based on a piston pump with precise control. Categorisation of drop formation into five types. Design of a two-step fluid flow profile for satellite-free drop production. Identification of the key parameters for optimal drop delivery of both Newtonian and Non-Newtonian fluids. Determination of the operating window for precise satellite-free drop formation. Abstract: A drop-on-demand liquid dispensing system, based on a rotary piston pump, for delivering microlitre droplets at ∼10 Hz is analysed. Five types of drop formation are observed under different pump operation schemes, characterised by the breakup behaviour of the thin liquid ligament that develops between the forming drop and the liquid remaining at the dispensing nozzle. A range of control parameters and fluids (Newtonian and non-Newtonian) have been explored in order to identify key system parameters for precise satellite-free drop formation and hence to establish an operating window. Under a conventional 'one-step-ejection' pump operation cycle, the window for satellite-free drop production is found to be small and impractical due to the long ligament and large pendant drop at the nozzle. The satellite-free operating window can be expanded dramatically with the ligament and pendant drop size under control with a novel 'two-step-ejection' process, in which the drop is first partly grown, then allowed to settle, and then ejected via a second pulse of liquid from the pump. Rapid deceleration of the pump near the maximum flow rate at the end of the second pulse is essential for satellite-free drop production.