After wearing the micro nano armor, water droplets become liquid marbles. Northwestern Polytechnical University for map
Water is one of the most common substances on the earth. For many years, Professor Zang Duyang of Northwestern Polytechnical University has been studying water drops tirelessly. They put armor on water droplets to make them stable liquid marbles and eventually become ideal micro-bio/chemical reactors, which play an important role in cell culture.
Putting the armor on water droplets, everything changed.
A drop of rain falls from the sky to the ground and becomes an irregular pool under the action of gravity, which is almost the common sense of everyone. But sometimes, if there is fine dust on the ground, raindrops fall on it and roll in the dust, the raindrops wearing the dust coat will be able to maintain the shape of water droplets.
Based on this principle, Professor Zang Duyangs team uniformly wrapped a layer of micro- and nano-particles around the surface of the water droplets to wear armor for the water droplets. At this time, the water droplets will not immediately spread out and stick to the desktop, but become a liquid marble, which can not only keep the form rolling on the desktop, but also bounce around.
It is precisely because of this layer of non-wetting micro-nano armor, so that the water droplets have a normal shape, which makes it possible to manipulate and transfer water droplets. The stable liquid marbles can be used as ideal microbiological / chemical reactors.
Compared with ordinary Petri dishes, this three-dimensional reactor has great advantages. For example, cell culture - in traditional Petri dishes, cells often grow in two dimensions, and there is a risk of contamination in contact with the vessel wall; in the three-dimensional reactor of water droplets, cells can grow in three dimensions without touching the vessel wall.
Professor Zangs team has cooperated with Monash University in Australia to culture mouse embryonic stem cells in liquid marbles and successfully cultivate three-dimensional cardiomyocytes.
Ultrasonic hand, manipulating water droplets to be invisible.
Under the long-term guidance of Academician Wei Bingbo and Professor Dominic Langevin of Sacramento University in Paris, France, Professor Zangs team has innovatively carried out the research of controlling water droplets by sound field.
In the sound field, water droplets are suspended steadily, as if they were lifted by an invisible hand. Ultrasound suspension provides the possibility of manipulating water droplets - Professor Zang led the students to explore and try.
Not only can open the door, but also close the door -- this operation is completely reversible. By adjusting the intensity of sound field, the opening and closing of micro nano layers on water droplets can be realized freely. What is the application meaning of this opening and closing? When liquid marbles are used as micro biochemical reactor, it is more convenient to extract and implant components from droplets by opening and closing doors, which makes it possible to control the internal reaction of droplets.
They also found that the coagulation of two or more droplets can be achieved by manipulating the sound field, i.e. two or more droplets in the sound field. By adjusting the intensity of the sound field, different droplets can be pulled together and merged into one.
What is the significance of this coagulation? It allows multiple droplets containing different reactants to merge together without any other external force, and accelerates the flow, mixing and reaction of droplets in the sound field. This method can overcome the disadvantages of traditional Petri dishes and manual operation, and is a new way of droplet fusion and induced reaction.
Sudden small bubbles open up new research directions.
Professor Zang has been using the sound field to manipulate water droplets and studying the principles and changes. Then one day, an unexpected visitor opened up a new direction for them.
In April 2013, two students of Chen Zang and Chen and Li Yuan were watching the droplets suspended in the sound field. In the blink of an eye, a strange thing happened. The water droplets which had been suspended very steadily disappeared. What floated in the sound field was actually a bubble, and the bubble was very stable and could be maintained for a long time.
The two did not let this change go, and immediately shot the video, and recorded the experimental parameters at that time, and reported to Zang, who was traveling abroad at that time. Funny! Very interesting! This is the first time when Zang saw bubbles.
Weve all seen blowing soap bubbles. If you dip a bubble stick in soapy water, a film of soapy water will appear in the whole crack of the stick, and then a series of bubbles can be blown out by pointing at the blow. This process is called instability in academics. In fact, its a long pocket that blows out. When the pocket is broken, one end of the opening closes to form a bubble.
However, the phenomenon of droplets transforming into bubbles under acoustic suspension can neither be explained by the theory of equilibrium shape of droplets in acoustic suspension, nor can we draw lessons from the existing phenomenon of droplet instability. How did bubbles come into being?
Teacher Zang, who was far away from home, urged the students to carry out research immediately, so that the students could repeat the experiment with different liquids and copy the process of producing bubbles. Then it was a painstaking study. In the face of a small bubble, Zang led the students to study for 5 years.
At first, the team analyzed it mechanically, but each time it felt close to the truth, it found that it was not the root of the problem. Again and again guess, verify, and again overturn, blink of an eye, 4 years later. In the fifth year of research, the team jumped out of the analysis of mechanics and finally found the perfect theoretical explanation of droplet-bubble phenomenon-resonance!
Under the condition of ultrasonic suspension, droplets can be pressed into thin liquid film by the intensity of sound field, and the film will be bowled when the sound field is continuously regulated. Once the bowl liquid film reaches the appropriate volume, it will resonate with the sound field and absorb the energy of the vibration source, which will cause the cavity to expand sharply and rapidly. Closed to form bubbles.
The most important discovery of this study is that the cavity surrounded by a curved acoustic suspension liquid film can be regarded as an acoustic resonator independent of the nature of the liquid. Once the curved liquid film cavity reaches the appropriate volume, whether by increasing the intensity of the sound field or dragging through the outside, it will produce ultrasonic resonance, and then suddenly expand to form bubbles.
The results provide new ideas and methods for the study of droplet dynamics manipulation, and can be used for reference in the preparation of shell-core soft materials, drug packaging and other fields. The research results, titled Inducing drop to bubbles transformation via Resonancein ultrasound, were published online in the top international journal Nature Communications on September 11. Western Polytechnic University is the first author and the only correspondent author of the paper. The collaborators are Monash University in Australia and Hull University in Britain.
What is the practical significance of such bubbles? We can try to make nanobubbles in this way, which have high activity and stability, and can play a great role in sewage treatment and so on. Zang said, It is also possible to arrange micro and nano particles orderly on the surface of such stable and uniform bubbles. When the bubbles break up, a new micro and nano material, bubbles, like amould, has a much better effect than using water droplets as amould.
Zang said that bubbles play an important role in peoples production and life. For example, in food processing, fermentation and expansion are the process of bubble formation. In many fields, such as pharmaceuticals, cosmetics, mineral flotation, the role of bubbles is also indispensable. The liquid bubbles realized by Zang Duyang Teacher Team through voice control technology have great potential in theoretical research and practical application.
When it comes to scientific research and studentsdemands, Zang repeatedly emphasizes two words: curiosity and execution. In Zangs view, finding problems and solving problems are equally important. To study the example of bubble, let Mr. Zang and his classmates remember deeply. In the experiment, many times, the students will dip the irregular and ugly water droplets in the sound field with a paper towel and squeeze them into another water droplet to do the experiment again. When the water droplets became bubbles, the students did not pass by the failure experiment. Their strong curiosity made them interested in the failure bubbles. They carefully recorded the strange phenomenon, guessed the principle behind it, began this extraordinary research, and after experiencing hardships. Abundant achievements have been achieved. It is curiosity and execution that make the principle behind a bubble come true. Source: China Youth Daily editor: Qiao Jun Jing _NBJ11279
When it comes to scientific research and studentsdemands, Zang repeatedly emphasizes two words: curiosity and execution. In Zangs view, finding problems and solving problems are equally important.
To study the example of bubble, let Mr. Zang and his classmates remember deeply. In the experiment, many times, the students will dip the irregular and ugly water droplets in the sound field with a paper towel and squeeze them into another water droplet to do the experiment again. When the water droplets became bubbles, the students did not pass by the failure experiment. Their strong curiosity made them interested in the failure bubbles. They carefully recorded the strange phenomenon, guessed the principle behind it, began this extraordinary research, and after experiencing hardships. Abundant achievements have been achieved.
It is curiosity and execution that make the principle behind a bubble come true.