"Creating a high-quality, stable resonator, as we have done, is usually complicated and requires many hours in the laboratory. But here, we saw it happen of its own accord, reacting to naturally occurring forces, and requiring no external energy input. You could practically make our resonator in your own kitchen—it is created at room temperature, with ordinary water and a little salt," explains research leader Timur Shegai, associate professor in the Department of Physics, who was himself surprised by the nature of the discovery in the lab.
When two tiny gold flakes—5000 nanometres in diameter and only 30 nanometres thick—meet in a salty aqueous solution, an interaction arises that causes them to form a pair. The two gold flakes are both positively charged as the aqueous solution covers them with double layers of ions. This causes a repelling electrostatic force, but, due to the simultaneous influence of the Casimir effect, an attracting force is also created and a stable balance arises, leaving a distance between the flakes of around 150 nanometres. The two nanoflakes orient themselves facing each other, with a cavity formed between them, and they remain stably in this arrangement for weeks of observations. The cavity then functions as an optical resonator, a device that provides many opportunities to explore various physical phenomena.
Once the gold flakes have formed a pair, they remain in place, and if not actively separated, more and more pieces of gold seek each other out and form a larger grouping. This means that the structure, purely through naturally occurring forces, can grow and create more interesting opportunities for researchers. The structure can be further manipulated by adding more salt to the aqueous solution, changing the temperature, or by illuminating it with lasers, which can lead to some fascinating observations.
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When two tiny gold flakes—5000 nanometres in diameter and only 30 nanometres thick—meet in a salty aqueous solution, an interaction arises that causes them to form a pair. The two gold flakes are both positively charged as the aqueous solution covers them with double layers of ions. This causes a repelling electrostatic force, but, due to the simultaneous influence of the Casimir effect, an attracting force is also created and a stable balance arises, leaving a distance between the flakes of around 150 nanometres. The two nanoflakes orient themselves facing each other, with a cavity formed between them, and they remain stably in this arrangement for weeks of observations. The cavity then functions as an optical resonator, a device that provides many opportunities to explore various physical phenomena.
Once the gold flakes have formed a pair, they remain in place, and if not actively separated, more and more pieces of gold seek each other out and form a larger grouping. This means that the structure, purely through naturally occurring forces, can grow and create more interesting opportunities for researchers. The structure can be further manipulated by adding more salt to the aqueous solution, changing the temperature, or by illuminating it with lasers, which can lead to some fascinating observations.
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