Fluid dynamic behavior of dispensing small droplets through a thin liquid film

• This paper presents a technology for dispensing droplets through thin liquid layers. The system consists of a free liquid film, which is suspended in a frame and positioned in front of a piezoelectric printhead. A droplet, generated by the printhead, merges with the film, but due to its momentum, passes through and forms a droplet that separates on the other side and continues its flight. The technology allows the dispensing, mixing and ejecting of picolitre liquid samples in a single step. This paper overviews the concept, potential applications, experiments, results and a numerical model. The experimental work includes studying the flight of ink droplets, which ejected from an inkjet print head, fly through a free ink film, suspended in a frame and positioned in front of the printhead. We experimentally observed that the minimum velocity required for the 80 pl droplets to fly through the 75 ± 24 lm thick ink film was of 6.6 m s-1. We also present a numerical simulation of the passage of liquid droplets through a liquid film. The numerical results for different initial speeds of droplets and their shapes are taken into account. We observed that during the droplet-film interaction, the surface energy is partially converted to kinetic energy, and this, together with the impact time, helps the droplets penetrate the film. The model includes the Navier- Stokes equations with continuum-surface-tension force derived from the phase-field/Cahn-Hilliard equation. This system allows us to simulate the motion of a free surface in the presence of surface tension during merging, mixing and ejection of droplets. The influence of dispensing conditions was studied and it was found that the residual velocity of droplets after their passage through the thin liquid film well matches the measured velocity from the experiment.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Strömningsmekanik och akustik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Fluid Mechanics and Acoustics (hsv//eng)

Nyckelord

Dispensing

Droplet

Fluid dynamic

Simulation

A-frames

Dynamic behaviors

Experimental works

Free liquid films

Free surfaces

Impact time

Initial speed

Ink droplets

Ink film

Inkjet print heads

Liquid droplets

Liquid sample

Numerical models

Numerical results

Numerical simulation

Potential applications

Print head

Residual velocity

Single-step

Small droplets

Surface energies

Tension force

Thin liquid film

Thin liquid layer

Experiments

Fluid dynamics

Fluids

Free flight

Ink

Liquid films

Navier Stokes equations

Numerical analysis

Surface chemistry

Surface tension

Drop formation

Fluid mechanics

Strömningsmekanik

Publikations- och innehållstyp

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