CN115554954A - Method for packaging liquid drops in bubbles driven by laser-induced cavitation collapse - Google Patents
Method for packaging liquid drops in bubbles driven by laser-induced cavitation collapse Download PDFInfo
- Publication number
- CN115554954A CN115554954A CN202211260950.9A CN202211260950A CN115554954A CN 115554954 A CN115554954 A CN 115554954A CN 202211260950 A CN202211260950 A CN 202211260950A CN 115554954 A CN115554954 A CN 115554954A
- Authority
- CN
- China
- Prior art keywords
- bubble
- bubbles
- cavitation
- liquid
- liquid drops
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
- B01J19/12—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing electromagnetic waves
- B01J19/121—Coherent waves, e.g. laser beams
Landscapes
- Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Optics & Photonics (AREA)
- Electromagnetism (AREA)
- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Physical Or Chemical Processes And Apparatus (AREA)
Abstract
The invention discloses an in-bubble liquid drop packaging method based on laser-induced cavitation. The liquid drops are generated only by the bubble jet caused by the collapse of the cavitation bubbles, and do not contact or enter the bubbles by other instruments, so that the generation process of the liquid drops is not polluted. The cavitation bubbles are the leading factor of the technology for driving the liquid drops to be packaged in the bubbles, the single cavitation bubbles can be generated by utilizing a laser induction method, meanwhile, the accurate positioning can be realized at the generation position, the operation difficulty is small, and the repeatability for packaging the liquid drops is high. According to the invention, no other energy is input, bubble jet flow and bubble state change are caused only by flow field pressure gradient change and pressure wave conduction near cavitation bubbles, and finally liquid drops are generated in the bubbles, so that the energy consumption required by the liquid drop generation process is low.
Description
Technical Field
The invention relates to the field of multiphase flow, in particular to an in-bubble liquid drop packaging method based on laser-induced cavitation.
Background
Fluid encapsulation is a physical phenomenon in which one fluid encapsulates another, and common fluid encapsulations can be divided into three main categories: "bubble in droplet", "droplet in droplet" and "droplet in bubble". At present, soap bubbles and the like are common in bubbles in liquid drops, emulsion and the like are common in liquid drops, but the packaging structure of the liquid drops in the bubbles is rare, particularly the packaging technology of the liquid drops by a thick air shell is still in a research stage, and a reliable and stable packaging method is not seen yet. The packaging method has great application potential, such as fine chemical engineering, medical drug and new material preparation.
At present, the method for encapsulating liquid drops in bubbles needs to enable instrument equipment to enter or contact the surfaces of the bubbles and inject the liquid drops into the bubbles, for example, a gas-liquid mixture in the bubbles is injected and encapsulated in the bubbles through a vertical needle tube, and the problems of easy pollution, high operation difficulty and poor stability exist in the operation. Wherein, when the bubble is spontaneously necked down from the vertical needle tube and separated from the vertical needle tube to generate the micro-jet liquid drop, the encapsulation effect of the liquid drop-wrapped bubble is generated with a certain probability, but the stable residence time of the liquid drop in the bubble is in millisecond level. The novel liquid drop packaging technology for stably generating liquid drops in bubbles is a research hotspot in the field of multiphase flow at present, and has important significance for potential applications such as medicine preparation, material processing, fluid transmission and the like, so that a novel packaging method capable of stably obtaining liquid drops in bubbles is urgently needed to be developed.
Disclosure of Invention
Aiming at the problems of easy pollution, complex process, poor repeatability and stability of the existing technology for packaging liquid drops in bubbles, the invention provides a method for packaging liquid drops in bubbles based on laser-induced cavitation collapse driving.
In order to achieve the purpose, the invention adopts the technical scheme that:
a solid with a super-hydrophobic coating is placed in a water body, and the super-hydrophobic coating with a patterned hydrophilic region is prepared on the surface of the solid and used for adhering underwater bubbles. The bubble can be attached to the solid surface through a three-phase contact line formed by the bubble near the boundary of the super-hydrophobic coating and the hydrophilic area, and the buoyancy, the surface tension and the gravity of the bubble are balanced at the moment.
After a plasma is formed above bubbles by focusing a laser to puncture a water body, cavitation bubbles are induced to be generated, and collapse is generated due to mass and heat transfer with surrounding water bodies after the cavitation bubbles are generated.
The bubble receives the transient pressure wave that cavitation bubble bursts the production, produces decurrent efflux in the inside one side that is close to the cavitation of bubble, forms the liquid column, when the efflux liquid column strikeed the bubble bottom, generates thicker efflux along the development of liquid column towards the bubble bottom at the same position that produces the bubble efflux, and top-down increases the thickness of liquid column.
The bubbles deform under the extrusion of a cavitation collapse pressure field, change from an initial spherical shape into an elliptical shape, and simultaneously compress the jet liquid column, so that the jet liquid column becomes thick. When instantaneous high pressure generated by collapse of the hollow bubble is dissipated, pressure around the bubble is gradually recovered, the elliptical bubble rebounds to be a spherical bubble under the action of surface tension, in the rebounding process, due to the continuity of a gas-liquid interface at the moment, the jet liquid column rebounds from a flat thick state to a thin and long state, the rebounding speed of the liquid column is smaller than that of the bubble interface under the action of gravity and the surface tension, necking is generated at one side close to the hollow bubble, and finally the liquid column is separated from the bubble interface to form irregular liquid drops.
The separated irregular liquid drops move to the bottom of the air bubble under the action of gravity and return to a spherical shape under the action of surface tension. Due to the superhydrophobicity of the solid surface, eventually rests inside the bubbles without fusion with the surrounding water body.
Compared with the prior art, the invention has the beneficial effects that:
(1) The liquid drops are generated only by the bubble jet caused by the collapse of the cavitation bubbles, and do not contact or enter the bubbles by other instruments, so that the generation process of the liquid drops is not polluted.
(2) The cavitation bubbles are the leading factor of the technology for driving the liquid drops to be packaged in the bubbles, the single cavitation bubbles can be generated by utilizing a laser induction method, meanwhile, the accurate positioning can be realized at the generation position, the operation difficulty is small, and the repeatability for packaging the liquid drops is high.
(3) According to the invention, no other energy is input, bubble jet flow and bubble state change are caused only by flow field pressure gradient change and pressure wave conduction near cavitation bubbles, and finally liquid drops are generated in the bubbles, so that the energy consumption required by the liquid drop generation process is low.
(4) The liquid drop in the invention can stay at the bottom of the bubble interior all the time stably, and is suitable for large-scale bubble-liquid drop preparation after being matched with an automatic displacement platform.
Drawings
FIG. 1 is a schematic view of a solid with a super-hydrophobic coating, wherein a patterned hydrophilic region on the surface of the solid is in a ring shape;
FIG. 2 is a schematic diagram of a solid with a super-hydrophobic coating, wherein a patterned hydrophilic region on the surface of the solid is in a linear shape;
FIG. 3 is a schematic view of a solid with a superhydrophobic coating, the patterned hydrophilic region on the surface of the solid being of a central ray type;
FIG. 4 is a schematic view of a device for droplet encapsulation in bubbles driven by laser-induced cavitation collapse;
FIG. 5 is a diagram of an experiment of droplet generation in a bubble when cavitation bubbles are not in contact with the bubble;
FIG. 6 is a graph comparing experiments with encapsulated droplets within bubbles with time intervals of six hours;
fig. 7 is a diagram showing an experiment of generation of droplets in a cavitation bubble when the cavitation bubble comes into contact with the bubble.
Reference numerals are as follows: 1. the solid with the super-hydrophobic coating comprises a super-hydrophobic coating area 2, a super-hydrophobic coating area 3, an annular patterned hydrophilic area 4, a linear patterned hydrophilic area 5, a central ray patterned hydrophilic area 6, cavitation bubbles 7, a water tank 8, a water body 9, liquid drops 10 and bubbles.
Detailed Description
The invention is further illustrated with reference to the following figures and examples.
As shown in fig. 1, 2 and 3, a superhydrophobic coating 2 having patterned hydrophilic regions, which may be an annular hydrophilic region 3, a linear hydrophilic region 4 and a central ray-type hydrophilic region 5, is prepared on the surface of a solid body 1. As shown in figure 4, a solid body 1 with a super-hydrophobic coating is statically placed in a water body 8 in a water tank 7, and a three-phase contact line formed by bubbles 10 near the boundary of the super-hydrophobic coating and a hydrophilic area enables the bubbles 10 to be attached to the surface of the solid body 1. After a laser is focused above bubbles to form plasma to puncture a water body, cavitation bubbles 6 are induced to be generated, the cavitation bubbles are collapsed due to mass and heat transfer with the surrounding water body after being generated, the change condition inside the bubbles is observed, bubble jet and bubble state change are caused by flow field pressure gradient change and pressure wave conduction near the cavitation bubbles, and finally liquid drops 9 are generated inside the bubbles.
The cavitation bubbles are any cavitation bubbles.
The cavitation generation mode can be laser induction or electric spark discharge.
The air bubbles are stably adhered to the surface of the solid and are any air bubbles.
The distance between the position of the cavitation bubble generation position and the initial distance of the attached bubbles needs to be ensured within the limit distance of jet interaction, and the cavitation bubbles can be directly contacted with the attached bubbles and also can keep a certain distance with the attached bubbles. The maximum radius R of the vacuole, and the limit distance D of the vacuole is less than or equal to 3.48R.
The fluid may be a Newtonian or non-Newtonian fluid.
As shown in fig. 5, cavitation bubbles were generated at t =0 μ s, starting to grow and expand, and cavitation bubbles at t =50 μ s grow to the maximum. Due to the presence of the bubble, the bubble starts collapsing and produces a jet directed away from the bubble, which ends with the first collapse at t =125 μ s, the jet moving away from the bubble with the bubble. During the first collapse process of the cavitation bubbles, the bubbles are subjected to transient pressure waves generated by collapse of the cavitation bubbles, t =75 μ s generates downward jet flow at one side of the bubble close to the cavitation bubbles, the jet flow moves towards the bottom of the bubbles until t =350 μ s, the jet flow of the bubbles reaches the bottom of the bubbles to form liquid columns connecting the upper end and the lower end of the bubbles, and collapse of the cavitation bubbles is finished at this time.
Meanwhile, thicker jet flow is generated at the same position where the bubble jet flow is generated and moves towards the bottom of the bubble along the liquid column, and the thickness of the liquid column is increased from top to bottom. the jet with the thickness of t =1.525ms reaches the bottom of the bubble and then continues to move downwards, but the upper half part of the liquid column connected with the top of the jet with t =2.776ms still keeps a column shape due to the blocking effect of the bottom, and the lower half part of the liquid column connected with the bottom is extruded into an oval shape from the column shape. Because the bubbles are extruded and deformed by a collapse pressure field of the cavitation bubbles, the bubbles are changed into an elliptical shape from an initial spherical shape, the bubble volume is the smallest at t =4.7ms, the elliptical shape is the flattest, and simultaneously, the jet liquid column is compressed, so that the liquid column is shortened and thickened, and at the moment, the liquid column is changed into a columnar shape again. When the instantaneous high pressure generated by the collapse of the air bubbles is dissipated, the pressure around the air bubbles is gradually recovered, and the elliptical air bubbles rebound into spherical air bubbles under the action of surface tension. In the rebound process, the jet flow liquid column rebounds from a flat thick shape to a long and thin shape due to the continuity of a gas-liquid interface, the rebound speed of the liquid column is smaller than that of a bubble interface, the liquid column is necked on one side close to a cavity under the action of gravity and surface tension, the contact area is gradually reduced, t =5.9ms is finally separated from the bubble interface, and irregular liquid drops are formed inside the bubbles. The separated irregular liquid drops move towards the bottom of the bubble under the action of gravity and return to a spherical shape under the action of surface tension, and meanwhile, t =11.0375ms finally stays at the bottom inside the bubble due to the hydrophobicity of the solid surface. Due to the flexibility and inertia of the bubbles, the bubbles continue to be stretched into a cone shape after being recovered to be spherical, the t =12.4275ms bubbles stretch to the longest, and the liquid drops staying at the bottom are also slightly stretched by the stretching of the bubbles. the t =18.6ms bubble returns to a spherical bubble, and the bubble is continuously and repeatedly circulated in the contraction and expansion process in the process of t =18.6-45.0375ms due to the oscillation frequency of the bubble, and finally the bubble is kept stable and unchanged. Although the liquid drops in the bubbles have slight oscillation, the oscillation intensity is far less than that of the bubbles, the liquid drops are kept at the same position at the tops of the bubbles and finally stand still in the bubbles without fusion with the surrounding water body due to the surface tension and the super-hydrophobicity of the solid surface. Fig. 6 is a comparative graph of experiments in which time intervals are different by six hours, which can show that the present invention can stably encapsulate liquid droplets inside bubbles, and has good stability.
By changing the distance between the cavitation bubbles and the bubbles, the cavitation bubbles are generated so as to be in contact with the bubbles, and the liquid droplets can be generated in the bubbles. As shown in fig. 7, cavitation bubbles t =0 μ s are generated, and when the cavitation bubbles contact the bubbles, the side of the bubbles close to the cavitation bubbles already generates a significant downward jet and starts to move toward the bottom. the cavitation bubble with t =50 mus begins to collapse and generates jet flow far away from the bubble, and the distance between the cavitation bubble and the bubble is very close, so that the change of the bubble surface is very violent during collapse, and the bubble begins to appear complex ripples from the lower surface to the upper surface in sequence. the t =125 mus bubble jet reaches the bottom of the bubble, forming a liquid column connecting the upper and lower ends of the bubble, and at the same time, the bubble near the side of the bubble begins to generate a thicker jet at the same position moving towards the bottom of the bubble. Because the distance between the cavitation bubbles is very close, the influence of the cavitation bubble collapse pressure field on the bubbles is very large, the whole bubbles are extruded and deformed by the pressure field and simultaneously can be twisted, the bubbles are changed into an elliptical shape from an initial spherical shape, simultaneously, the jet liquid column is compressed, firstly, the jet liquid column is thickened, t =3.2625ms is changed into a spherical shape from a column shape, secondly, the bubbles are twisted due to the influence of the violent cavitation bubble collapse pressure field to cause the jet liquid column to be thinned, t =5.1625ms is changed into a column shape from a spherical shape, and at the moment, the bubble volume is minimum. After instantaneous high pressure generated by collapse of the air bubble is dissipated, the pressure around the air bubble is gradually recovered, the elliptic air bubble rebounds to be a spherical air bubble under the action of surface tension, and the air bubble does not twist any more. In the rebound process, the jet flow liquid column begins to rebound to a slender shape due to the continuity of a gas-liquid interface, the rebound speed of the liquid column is smaller than that of a bubble interface, the liquid column is necked at one side close to a void bubble under the action of gravity and surface tension, the contact area is gradually reduced, t =6.475ms is finally separated from the bubble interface, and irregular liquid drops are formed inside the bubble. The separated irregular droplets move towards the bottom of the bubble under the action of gravity, and the droplets move to the bottom of the bubble with t =8.525 ms. At the same time, the t =11.5125ms droplet reverts to spherical under surface tension. Due to the flexibility and inertia of the bubbles, the bubbles can be stretched into a cone shape after being recovered to be spherical, t =12.5625ms is stretched to be the longest, and the liquid drops staying at the bottom can be slightly stretched. The bubbles slowly return to a spherical shape from a conical shape, and because of the own vibration frequency of the bubbles, the bubbles are continuously and repeatedly circulated in the process of reduction and expansion in the process of t =12.5625-31.0875ms, and finally keep stable and unchanged. The liquid drops in the bubbles have slight oscillation, but the oscillation intensity is far less than that of the bubbles, and the liquid drops are kept at the same position at the bottoms of the bubbles and finally stand still inside the bubbles due to the surface tension and the super-hydrophobicity of the solid surfaces. Unlike fig. 3, t =9.7125ms irregular drops are extruded into a smaller drop during stretching, the small drop moves freely in the bubble (t =9.7125-27.9375 ms), t =27.9375ms drops enter the bubble surface and disappear, but the large drop stays at the bottom of the bubble more stably without fusion with the surrounding water body due to the super-hydrophobicity of the solid surface.
In summary, the present invention utilizes the change of the pressure field in the water body caused by the collapse of the cavitation bubbles to make the bubbles impacted by the jet flow, so as to achieve the purpose of generating the liquid drops in the bubbles, and the liquid drops can stably stay in the bubbles.
The present invention is not limited to the above embodiments, and all equivalent changes and modifications made within the scope of the present invention should be covered by the present invention.
Claims (4)
1. A method for packaging liquid drops in bubbles driven by laser-induced cavitation collapse is characterized by comprising the following steps:
placing a solid with a super-hydrophobic coating in a water body, and preparing the super-hydrophobic coating with a patterned hydrophilic region on the surface of the solid for adhering underwater bubbles; the bubble can be attached to the solid surface through a three-phase contact line formed by the bubble near the boundary of the super-hydrophobic coating and the hydrophilic area, and the buoyancy, the surface tension and the gravity of the bubble are balanced at the moment;
after a laser is focused above bubbles to form plasma to puncture a water body, cavitation bubbles are induced to be generated, and the cavitation bubbles are collapsed due to mass transfer and heat transfer with surrounding water bodies after being generated;
when the jet liquid column impacts the bottom of the bubble, thicker jet flow is generated at the same position where the bubble jet flow is generated and develops towards the bottom of the bubble along the liquid column, and the thickness of the liquid column is increased from top to bottom;
the air bubbles deform under the extrusion of a cavitation collapse pressure field, change from an initial spherical shape into an elliptical shape, and simultaneously compress a jet flow liquid column to cause the jet flow liquid column to become thick; after instantaneous high pressure generated by collapse of the air bubbles is dissipated, the pressure around the air bubbles is gradually recovered, and the elliptic air bubbles rebound to spherical air bubbles under the action of surface tension; in the rebound process, due to the continuity of the gas-liquid interface at the moment, the jet flow liquid column rebounds from a flat and thick shape to a slender shape, the rebound speed of the liquid column is lower than that of the bubble interface under the action of gravity and surface tension, the side close to the vacuole is necked down, and finally the liquid column is separated from the bubble interface to form irregular liquid drops;
the separated irregular liquid drops move to the bottom of the bubbles under the action of gravity and recover to be spherical under the action of surface tension; due to the super-hydrophobicity of the solid surface, the solid surface is finally static in the air bubble without fusion with the surrounding water body, and therefore the liquid drop encapsulation in the air bubble is completed.
2. The method for encapsulating the droplet in the bubble driven by the laser-induced cavitation collapse as claimed in claim 1, wherein: the cavitation bubble generation mode can also adopt electric spark discharge.
3. The method for encapsulating the droplet in the bubble driven by the laser-induced cavitation collapse as claimed in claim 1, wherein: the initial distance between the position of the cavitation bubble generation and the attached bubble is required to be ensured within the limit distance of jet interaction.
4. The method for encapsulating the droplet in the bubble driven by the laser-induced cavitation collapse as claimed in claim 3, wherein: the limit distance D is less than or equal to 3.48R, and R is the maximum radius of the cavitation bubbles.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211260950.9A CN115554954A (en) | 2022-10-14 | 2022-10-14 | Method for packaging liquid drops in bubbles driven by laser-induced cavitation collapse |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211260950.9A CN115554954A (en) | 2022-10-14 | 2022-10-14 | Method for packaging liquid drops in bubbles driven by laser-induced cavitation collapse |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN115554954A true CN115554954A (en) | 2023-01-03 |
Family
ID=84745566
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211260950.9A Pending CN115554954A (en) | 2022-10-14 | 2022-10-14 | Method for packaging liquid drops in bubbles driven by laser-induced cavitation collapse |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115554954A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116237101A (en) * | 2023-03-20 | 2023-06-09 | 哈尔滨工程大学 | Micro-droplet generation device and micro-droplet generation method based on bubble necking effect |
-
2022
- 2022-10-14 CN CN202211260950.9A patent/CN115554954A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116237101A (en) * | 2023-03-20 | 2023-06-09 | 哈尔滨工程大学 | Micro-droplet generation device and micro-droplet generation method based on bubble necking effect |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Leng | Splash formation by spherical drops | |
| CN115554954A (en) | Method for packaging liquid drops in bubbles driven by laser-induced cavitation collapse | |
| Zhang et al. | Satellite formation during coalescence of unequal size drops | |
| CN108722326B (en) | Vibration assembly, beauty device with vibration assembly and using method of beauty device | |
| Yang et al. | Multitude of dimple shapes can produce singular jets during the collapse of immiscible drop-impact craters | |
| Zhang et al. | EHD effects on periodic bubble formation and coalescence in ethanol under non-uniform electric field | |
| Siddique et al. | Jet ejection following drop impact on micropillared hydrophilic substrates | |
| Luo et al. | Collapse of cavitation bubbles near air bubbles | |
| CN106273491A (en) | The controlled ultrasonic droplet ejection of spray angle increases material and manufactures device and method | |
| Dadvand et al. | A note on spark bubble drop-on-demand droplet generation: simulation and experiment | |
| CN206935332U (en) | The microlayer model active preparation facilities of flow focusing jet disturbing type is driven based on liquid | |
| EP2852953B1 (en) | Localised energy concentration | |
| Cui et al. | Experimental studies of bubble dynamics under a broken horizontal plate | |
| Raman et al. | Microemulsification from single laser-induced cavitation bubbles | |
| CN106142571A (en) | The ultrasonic droplet ejection of the many materials of infinitely variable speeds increases material and manufactures device and method | |
| EP3202491A1 (en) | Anti-bubble generator | |
| Huang et al. | Wall vortex induced by the collapse of a near-wall cavitation bubble: Influence of the water surface | |
| US10384218B2 (en) | Liquid atomization method and device | |
| CN107100831A (en) | The microlayer model active preparation facilities and method disturbed based on piezoelectric circular | |
| Karri et al. | Jets and sprays arising from a spark-induced oscillating bubble near a plate with a hole | |
| CN108607376B (en) | Liquid drop fusion method and device based on oscillatory flow | |
| Tian et al. | Effects of the electric field on the overall drop impact on a solid surface | |
| CN107029640A (en) | The microlayer model active preparation facilities and method of flow focusing jet disturbing type are driven based on liquid | |
| Krishnan et al. | Impact of freely falling liquid containers and subsequent jetting | |
| Shervani-Tabar et al. | A numerical and experimental study of a collapsing bubble-induced droplet ejector |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |