Coffee is dripped on the table, so scientists have discovered the method of detecting malaria

In life, everyone will accidentally overthrow coffee, tea, and drinks. While busy, I don’t know if you notice such a magical phenomenon -if you accidentally overturn, or drop the coffee to drop the coffee to On the desktop, after it is dry, the stains formed will be a dark -colored, light -colored ring inside.

Source ｜ Baidu Picture

Different from transparent pure water, brewed drinks such as coffee and tea can be classified as a solution (strictly a mixture of solution and suspension liquid) in a sense It shows its color.

Taking the coffee that everyone often drinks as an example, its dark brown comes from the charcoal black substances that coffee beans are roasted and extracted. After coffee brew, these substances become several small particles suspended in liquid. We accidentally dripped on clothes or coffee stains and tea stains on the desktop. Although the color of these stains is caused by small particles, what makes these small particles eventually become a ring?

Source ｜ Xinhuanet

1

How do people know the coffee ring effect

For most ordinary people, the coffee ring effect is just an accidental phenomenon in life. But in the eyes of physicists, there is a mystery behind this. In 1997, physicists at the University of Chicago, Sidney Nago, and Thomas Willteng and others published a paper on the "Coffee Ring effect" in the "Nature" magazine.

In this article, the coffee ring effect was officially described for the first time, but the focus of this paper is concentrated in the suspended spherical particles. Later, with the continuous deepening of similar research, people gradually learned the role of suspended particles. Then, the research results on how to break the "coffee ring effect" have continued to appear. For example, the team of physicists at the University of Pennsylvania hopes to change the granular shape of the solution to destroy the coffee ring effect and find a new method to achieve uniformly deposited solid granular layers.

Source | Baidu Encyclopedia

2

What causes the coffee ring effect

Although the coffee ring effect is named after coffee, in a broad sense, it should be a phenomenon that "solution" occurs when the solid surface evaporates. The formation process of the formation of the colorful ring represented by the coffee ring is also more intuitive: when the solution droplets are dripping on the desktop or paper, the droplet evaporation will not form a circle that is gradually narrowed and gradually shrinks. It is a circular shape that forms a large number of outer soluble particles and less internal solution particles.

Source | Chemical Instrument Network

This is because when the water in the droplets evaporates, the interaction of the solid fluid interface between the desktop and the liquid and the air surface of the liquid and the air surface is different, resulting in the different evaporation rate of water in different positions of the droplets, which prompts to promote the promotion of the water droplets, which prompts to promote the promotion of the water. The formation of the coffee ring. At the interface between the desktop or paper and the droplet, the evaporation rate of water is faster than the evaporation of water at the interface between the droplet and the air. The particles come to the edge of the droplet and the desktop or paper surface to supplement. After the water was evaporated, the soluble particles kept accumulating on the edges and became "ring".

Source | Baidu Encyclopedia

3

Large use behind small discovery

The coffee ring effect is not only an interesting small phenomenon in life. Its appearance actually brings some annoying troubles to people's production and life. For example, the inkjet of the printer is also the manifestation of the coffee ring effect.

To solve this problem, scientists began to find how to form a uniform solid layer after the droplet evaporation. Later, they discovered that if they want to solve this phenomenon, they need to change the nature of the suspended particles. Scientists have found different granules to change the properties of the film on the interface of air and liquid, which affects the evaporation process.

Under the same conditions, oval particles will change the interface of air and liquid. Although this research is not yet fully mature, scientists are still committed to removing the research of "coffee ring effects" by changing the shape of the suspended particles. But this discovery directly reveals the effect of granular shape on evaporation, and effectively guide people to improve the method of printing and painting.

Scientists study different shapes of particles on evaporation

Source | "Control of Droplet Evaporation on Oil-Coated Surfaces for The Synthesis of"

In addition, the coffee ring effect is still "sparkling" in the field of biology and medical care. In medical diagnosis, scientists combine the "coffee ring effect" with biosensor technology to detect biological biological in the body fluids such as saliva, blood and blood landmark. Researchers at the University of Van Derbolt developed a method of rapid detection of malaria on this basis.

As a kind of intense infectious disease, how to quickly detect malaria is an important means to prevent and treat the spread of infectious infectious. In this detection method, researchers add three particles to the liquid to be tested (red fluorescence can be emitted, green fluorescence can be emitted, but magnetic but cannot emit fluorescence). When the droplets containing these three particles are dry under the action of the magnetic field, the two particles that can emit fluorescence will gather on the edge of the droplet, showing a yellow ring stacked from green and red light. Magnetic particles will have a chemical reaction with a special protein secreted by the pathogen somatoscopy and connect with green fluorescent particles. Both of the colored particles will be left, showing the red cylinder of the red ring. Display whether there are Plasmodium infections. Source | "Science World"

Not only that, the coffee ring effect also allows people to pay attention to the separation of the same solution in the same solution according to the different particle size, such as the smallest diameter of the outer particles concentrated on the coffee ring, and the diameter of the inner side of the coffee ring is larger. Use this principle to achieve material separation.

Newton was smashed by Apple, and then began to pay attention to the gravity; perhaps the mystery of science is also hiding in these subtle phenomena in life. Next time you drink coffee, if you accidentally drip on the table, you may wish to wipe it cleanly and imagine the new application of the coffee ring effect.

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