Colloidal Droplet Impinging and Freezing on an Inclined Surface
ORAL
Abstract
Inkjet-based three-dimensional (3D) printing has been well developed as an additive manufacturing technique. In this technology, a mixture of solvent containing small particles of printing materials is used as the inkjet solution. In practice, a series of inkjet droplets are released from a programmed nozzle onto a printing surface. After the drying process, the solvent is removed, and the printing materials remain on the substrate to form solid structures as designed.
It was found that during traditional drying processes such as evaporation, internal flows in droplets transport solid particles from the center of a sessile droplet toward its boundary, causing a non-uniform distribution of printing materials within the printing region on substrates. To improve the printing quality of patterns with uniform material distribution on substrates, we have developed a novel freezing-sublimation-based 3D printing method. It minimizes undesired particle motion in droplets during the drying process by rapidly freezing the droplets on the substrate after ink jetting and then removing the frozen liquid solvent through sublimation.
We experimentally proved that the suggested method could provide a "lock effect" on solid particles in inkjet droplets during printing. However, the shape of the droplets during the freezing process also played a role. For example, when the substrate surface was not placed horizontally, and when the freezing rate of the impinging droplet was relatively slow, the droplet formed a crescent-shaped spreading pattern with uneven thickness due to gravitational effects. This could lead to solid particle aggregation in regions where the frozen droplet had greater local thickness.
We conducted follow-up experiments using substrates mounted on an angle-adjustable stage to study how the freezing rate of droplets and the inclined angle of substrates affect particle distribution of printed patterns. The experimental observations and subsequent theoretical analysis suggested that droplet motion was influenced by both the freezing process and the dynamic process of droplet spreading on substrates. The results of this study can expand the capability of the freezing-sublimation-based 3D printing method under varied substrate conditions.
It was found that during traditional drying processes such as evaporation, internal flows in droplets transport solid particles from the center of a sessile droplet toward its boundary, causing a non-uniform distribution of printing materials within the printing region on substrates. To improve the printing quality of patterns with uniform material distribution on substrates, we have developed a novel freezing-sublimation-based 3D printing method. It minimizes undesired particle motion in droplets during the drying process by rapidly freezing the droplets on the substrate after ink jetting and then removing the frozen liquid solvent through sublimation.
We experimentally proved that the suggested method could provide a "lock effect" on solid particles in inkjet droplets during printing. However, the shape of the droplets during the freezing process also played a role. For example, when the substrate surface was not placed horizontally, and when the freezing rate of the impinging droplet was relatively slow, the droplet formed a crescent-shaped spreading pattern with uneven thickness due to gravitational effects. This could lead to solid particle aggregation in regions where the frozen droplet had greater local thickness.
We conducted follow-up experiments using substrates mounted on an angle-adjustable stage to study how the freezing rate of droplets and the inclined angle of substrates affect particle distribution of printed patterns. The experimental observations and subsequent theoretical analysis suggested that droplet motion was influenced by both the freezing process and the dynamic process of droplet spreading on substrates. The results of this study can expand the capability of the freezing-sublimation-based 3D printing method under varied substrate conditions.
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Presenters
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Haipeng Zhang
City College of New York, Department of Mechanical Engineering, City College of New York, New York, NY 10031
Authors
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Yang Liu
City College of New York, Department of Mechanical Engineering, City College of New York, New York, NY 10031
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Haipeng Zhang
City College of New York, Department of Mechanical Engineering, City College of New York, New York, NY 10031
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Xiaoxiao Zhang
City College of New York