The results of this strange phenomenon can be applied to many industries.
Have you ever seen the sight of tiny water droplets rolling gently on the surface of the water? When it rains or when you pour some fresh milk into a cup of coffee? Astronomers have just found an explanation for this strange physical phenomenon: it only occurs under certain conditions.
According to researchers at the Massachusetts Institute of Technology, in order for a water droplet to float on the surface of a solution for a short time before entering the solution below, the temperature between them must be different. In this latest study, they also found a way to control this phenomenon.
In the vast majority of cases, if two types of solution – of the droplet and the solution below – are of the same type, they will immediately mix. But when there is a drop of water still floating and rolling on the surface of the solution, it turns into ” noncoalescence “. And yet, it also has great uses in science.
By figuring out why this “non-fusion” occurs, we can develop more effective emulsifiers, such as medicines, makeup or paints. This strange phenomenon can also be studied and applied to technologies such as microfluidic channel chips (which allow control of activity on a very small scale through one or more small channels with small sizes). more than 1mm): water particles can carry reagents to the required locations on the surface of a chip.
For that reason, the phenomenon of “non-consolidation” has been studied for some time. They were also able to reproduce this phenomenon in a variety of ways – water particles with the opposite electrical charge to the solution would also do the same.
They also learned what factors influence the “unconsolidation”. For example, the viscosity of the solution, the surface tension, the height of the drop when it falls, the electricity and the size of the water particles all play a certain role in the formation of water particles on the surface of the solution and the time it takes. its existence.
After all that previous research, the question of WHY remains and exactly how to control it remains unclear.
However, a study in 1996 showed the effect of temperature on solution non-consolidation. Based on that premise, MIT graduate student Michela Geri led a team of researchers that conducted a mathematical experiment that identified temperature differences in this strange phenomenon.
“Based on our new hypothesis, the engineers were able to determine the critical temperature difference required to separate the water particle and the solution surface, and also determine the maximum weight of the liquid. water so that it can float,” said Geri.
” If you understand the basics, you can start designing things the way you want.”
And to do this experiment, Geri created a box with a metal bottom, filled it with silicone oil, and placed the whole thing on a heating device – which can heat, cool or retain heat. Ms. Geri uses a syringe, pouring on the surface of the solution a bead of water, which is also silicone oil.
Example of a thermal platform/hot-cold plate used in the above test.
The test is carried out with a wide range of temperatures, different oil viscosity levels and concentrations. The researchers used a high-speed camera to record the experiment, with footage of 2,000 frames per second, to closely observe the drop’s interaction with the liquid’s surface.
The results showed that the higher the separation temperature, the greater the chance of non-fusion. With a difference of 30 degrees Celsius, Ms. Geri was able to keep the water particle in the “unfused” state for about 10 seconds. This is because the difference in temperature creates convection – the flow of air that coats the water droplets and coats the surface of the solution. The higher the temperature, the stronger this convection flow, which will prevent water particles from entering the solution below.
The results of this experiment will be carefully studied, to know how rainwater disperses chemicals and biological substances.
The team’s research was published in the Journal of Fluid Mechanics.