New study showed that quantum dots (QDs) or nanosized semiconducting crystals could be arranged using a new method.

Nanowerk describes quantum dots as man-made nanoscale crystals that can transport electrons.

According to a report, if spilled coffee is not wiped off right away, it leaves a stain behind where the edges become darker than the rest.

According to the POSTECH research team, this simple approach is facilitating the development of display panels with a maximum of 20 times higher resolution than the conventional ones.

The team was led by the Department of Mechanical Engineering and Chemical Engineering's by Professor Junsuk Rho; the Division of Advanced Nuclear Engineering and Department of Mechanical Engineering's professors HangJin Jo and Moo Kwan Kim; and the Department of Mechanical Engineering PhD candidate Jaebum Noh.

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Science Times - Coffee Ring Effect: Researchers Develop New Approach for Arranging Quantum Dots in the Form of Very Tiny Pixels
(Photo : Prof. Michael S. Wong on Wikimedia Commons )
CdSe Quantum Dots

QD Array Developed Using the Phenomenon

The research team developed a quantum dot array by using a phenomenon that takes place when a suspension evaporates.

Suspension pertains to a liquid in which solid particles are spread and suspended in ink, paint, or muddy water. Essentially, QDs, which are numerous nanometers in size, are following fluid flow very well.

Just like coffee stains are left with a drop is running on the side of a cup, when suspension containing QDs evaporates, the particles automatically assemble in particular areas like the edge of a liquid drop where the capillary flow induces.

Numerous attempts have been made to take advantage of such a property, although acquiring brightness suitable for displays has been quite a challenge.

QDs Arranged in a Form of Tiny Pixels

In the study titled Pixelated Microsized Quantum Dot Arrays Using Surface-Tension-Induced Flow, published in ACS Applied Materials and Interfaces, the study authors specified that the cost of the product was high as well since QDs were printed "directly on the substrate" through the use of expensive equipment.

To address this said limitation, the study investigators arranged the QDs in a form of extremely tiny pixels during the suspension evaporation process by using a V-shaped structure.

In addition, when the liquid gets poured and evaporated, the quantum dots are driven in the direction of the tip of the V-shape and mount up there.

Results of the study showed that the brightness of the quantum dot pixels in this manner was 2 times brighter than that of the control group. Results have also shown a high uniformity rate of more than 98 percent.

According to professors Rho and Jo, recently, the home appliance industry is utilizing CDs in color filters in televisions to produce bright and natural images.

They added that through the quantum dot pixel array approach developed in this particular research, bright QD pixels are developed by simply spraying the suspension minus expensive equipment, therefore decreasing the cost for manufacturing.

Related information about the coffee ring effect is shown on And You Know's YouTube video below:


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