The smallest coffee ring will be used to detect the disease

Release date: 2010-06-09


When the coffee ring effect splashes the coffee on the table, paying attention to the mark left by the coffee droplets after the liquid evaporates, it will be found that the peripheral position of the droplet forms a dark ring that is much darker than the middle area, which means that it is in the peripheral position. The concentration of small particles of coffee deposited is much higher than the concentration in the middle. This phenomenon of uneven deposition is referred to as the "coffee ring effect."
Not only coffee, but many solutions with solid small particles will have a similar dark ring at the boundary after evaporation of the liquid. The research team at the Cell Control Institute of the University of California, Los Angeles, suggests that this common phenomenon in life can be combined with biosensing technology to detect biomarkers in various body fluids such as saliva, blood, etc. for medical diagnosis. However, to achieve this idea in highly sensitive bioassays, it is first necessary to find the minimum size limit for the appearance of the coffee ring effect.
The reason why the coffee ring effect has a size limit is that as the droplet size decreases, the speed of droplet evaporation increases greatly, but the velocity of the particles in the droplet does not change so fast, if the droplet size To a certain extent, the rate at which the droplets evaporate will be much greater than the velocity of the particles. Before the droplets evaporate, the particles do not have enough time to precipitate into a ring structure. These small particles, which are too late to move, are deposited nearly uniformly over the entire surface covered by the droplets rather than the edge regions of the droplets.

For bioassays Researchers have created a special lattice structure surface. Adjacent grids have different hydrophilic and hydrophobic properties due to the different coatings applied, ie the ability to retain liquid or repel liquid at different locations on the surface. With such a structure, droplets of a desired size can be formed on the surface.
The researchers then attempted to dissolve different sizes of latex particles in water, which were between 20 and 100 nanometers in diameter, which is the size of the biomarker small particles typically detected by biosensors. Next, they dripped the solution in which the small particles were dissolved onto the prepared plane, tilting the surface to make the excess liquid slip behind, and forming a droplet of the desired diameter on the lattice of the hydrophilic surface. The researchers conducted a number of experiments to gradually reduce the droplet size until the coffee ring effect no longer appeared. For small particle solutions with a diameter of 100 nanometers dissolved, the coffee ring effect no longer occurs when the droplet size is reduced to nearly 10 microns.
Researchers say that human blood or saliva contains a large number of micron-nano-scale molecules or biological particles that can be deposited using coffee ring effects and analyzed and quantified using relevant bioassay techniques to understand the so-called coffee ring effect. The smallest possible size that appears helps guide people to reduce the size of the biosensor as much as possible. This detection technique also has the advantage that the entire inspection process relies only on the normal evaporation process and does not require the consumption of electrical energy and other complicated techniques, which makes the entire inspection facility very inexpensive and easy to manufacture. For remote areas that do not have enough medical equipment, such inexpensive and easily accessible medical devices will be of great help to related medical tests.
Researchers are currently using the physical mechanisms of the research to adjust the relevant parameters, hoping to get the best combination of experimental conditions, so that the coffee ring effect is used in biological detection technology.

Source: Pharmaceutical Economics

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