A method to control droplet impact shape, contact time and droplet splitting

Abstract

The invention discloses a method for controlling droplet impact shape, contact time and controllable splitting of droplet, comprising the following steps: step 1, template design; step 2, template fabrication; step 3, template surface treatment; step 4, liquid Droplet impact; step five, observation and analysis of impact morphology and dynamics. By changing the shape, size, number, position of obstacles on the template, and the impact position of the droplet, various impact dynamics can be obtained, and the boundary between spreading and retraction can be broken, so that the spreading and Retraction coexists, and by controlling the impact dynamics of different forms, the goals of reducing contact time, variable and controllable single droplet impact forms, and controllable splitting during droplet impact are achieved. The method is simple to operate, low in cost and good in effect, and can be applied to fields such as self-cleaning, printing, open microfluidics, food and drug subpackaging and transmission.

Description

technical field

[0001] The invention relates to the technical field of droplet collision, in particular to a method for controlling droplet collision shape, contact time and controllable splitting of droplet. Background technique

[0002] The impact of liquid droplets on solid surfaces has important applications in many fields, such as inkjet printing, paint spraying, pesticide spraying, fire protection and heat transfer, food packaging and other fields. In the last ten years, the impact of water droplets hitting superhydrophobic surfaces has attracted widespread attention. This is because the extremely low surface energy of superhydrophobic surfaces makes water droplets have little energy dissipation during impact and can bounce quickly (millimeter-level water droplet impact The contact time is about 12 milliseconds), so it has been applied in self-cleaning, anti-icing, anti-bacteria and other fields. Therefore, scientists have tried every means to reduce its contact time,...

Examples

Embodiment 1

[0032] The method for controlling droplet impact form in the present embodiment comprises the following steps:

[0033] (1) Template design: Firstly, the template of 1~4 ball obstacles is designed by 123Ddesign software. The template is a 3*3cm square and a flat plate with a thickness of 3 mm. The obstacle balls have a radius of 0.5 mm and are distributed in the form of hemispheres. On the surface of the plate, and the gap in the middle of the ball is close to the size of the water drop, that is, 2.4~2.6 mm;

[0034] (2) Template making: use a 3D small square printer to print out the template, and print a blank template for comparison; the printing ink used is the polymer ink provided by Formalabs;

[0035] (3) Template surface treatment: After the template is printed, let it dry naturally, and evenly brush the hydrophobic liquid once or twice on the surface of the template plate and obstacles with a brush, and the superhydrophobic template will be obtained after the solvent e...

Embodiment 2

[0041] The method for controlling the contact time of droplet impact in this example, steps (1) template design, (2) template making and (4) droplet impact experimental conditions are the same as in Example 1, taking the center of the water droplet impacting 2 balls as an example, due to the impact The anisotropic characteristics of the time make its momentum concentrated in one direction, so the contact time can be reduced. The impact velocity of water droplets is controlled to be 0.6 m s -1 , 0.75 m s -1 , 0.88 m s -1 , the contact time varies with the distance between the balls as image 3 As shown, when the distance between the balls is less than 3 mm, the contact time of the water droplet hitting the ball obstacle template is reduced to about 6 ms compared with the planar blank superhydrophobic template, which is about 50% lower. As the distance between the balls increases, the contact time gradually increases until the distance increases to 5.6 mm, and the contact tim...

Embodiment 3

[0043] In this embodiment, the method for controlling droplet impact and splitting is the same as that of Example 1, the steps (1) template design, (2) template making, and (4) droplet impact experiment conditions are the same as in Example 1, and the number of obstacle balls is 1, 2, 3, 4, 5, 6, ... on the template, control different impact speeds, then get different split times i in the exit direction, plus the small water droplets left in the center, the super Hydrophobic template, the number of split droplets obtained is m=n*i+1 (where n is the number of small ball obstacles, i is the number of splits in each exit direction, and m is the total number of split droplets) . In this way, the direction and number of droplet splitting can be controlled, such as Figure 4 shown.

[0044] The above method can control the splitting direction and number of water droplets, but it is found during the experiment that continuous operation cannot be realized due to the existence of sma...

technical field

[0001] The invention relates to the technical field of droplet collision, in particular to a method for controlling droplet collision shape, contact time and controllable splitting of droplet. Background technique

[0002] The impact of liquid droplets on solid surfaces has important applications in many fields, such as inkjet printing, paint spraying, pesticide spraying, fire protection and heat transfer, food packaging and other fields. In the last ten years, the impact of water droplets hitting superhydrophobic surfaces has attracted widespread attention. This is because the extremely low surface energy of superhydrophobic surfaces makes water droplets have little energy dissipation during impact and can bounce quickly (millimeter-level water droplet impact The contact time is about 12 milliseconds), so it has been applied in self-cleaning, anti-icing, anti-bacteria and other fields. Therefore, scientists have tried every means to reduce its contact time,...

Examples

Embodiment 1

[0032] The method for controlling droplet impact form in the present embodiment comprises the following steps:

[0033] (1) Template design: Firstly, the template of 1~4 ball obstacles is designed by 123Ddesign software. The template is a 3*3cm square and a flat plate with a thickness of 3 mm. The obstacle balls have a radius of 0.5 mm and are distributed in the form of hemispheres. On the surface of the plate, and the gap in the middle of the ball is close to the size of the water drop, that is, 2.4~2.6 mm;

[0034] (2) Template making: use a 3D small square printer to print out the template, and print a blank template for comparison; the printing ink used is the polymer ink provided by Formalabs;

[0035] (3) Template surface treatment: After the template is printed, let it dry naturally, and evenly brush the hydrophobic liquid once or twice on the surface of the template plate and obstacles with a brush, and the superhydrophobic template will be obtained after the solvent e...

Embodiment 2

[0041] The method for controlling the contact time of droplet impact in this example, steps (1) template design, (2) template making and (4) droplet impact experimental conditions are the same as in Example 1, taking the center of the water droplet impacting 2 balls as an example, due to the impact The anisotropic characteristics of the time make its momentum concentrated in one direction, so the contact time can be reduced. The impact velocity of water droplets is controlled to be 0.6 m s -1 , 0.75 m s -1 , 0.88 m s -1 , the contact time varies with the distance between the balls as image 3 As shown, when the distance between the balls is less than 3 mm, the contact time of the water droplet hitting the ball obstacle template is reduced to about 6 ms compared with the planar blank superhydrophobic template, which is about 50% lower. As the distance between the balls increases, the contact time gradually increases until the distance increases to 5.6 mm, and the contact tim...

Embodiment 3

[0043] In this embodiment, the method for controlling droplet impact and splitting is the same as that of Example 1, the steps (1) template design, (2) template making, and (4) droplet impact experiment conditions are the same as in Example 1, and the number of obstacle balls is 1, 2, 3, 4, 5, 6, ... on the template, control different impact speeds, then get different split times i in the exit direction, plus the small water droplets left in the center, the super Hydrophobic template, the number of split droplets obtained is m=n*i+1 (where n is the number of small ball obstacles, i is the number of splits in each exit direction, and m is the total number of split droplets) . In this way, the direction and number of droplet splitting can be controlled, such as Figure 4 shown.

[0044] The above method can control the splitting direction and number of water droplets, but it is found during the experiment that continuous operation cannot be realized due to the existence of sma...

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