The problem with atoms is that they’re small. Too small. Don’t you wish they were... bigger?
There’s an entire field of research, known as colloidal science, that attempts to study atoms by making larger analogues for them. Scientists create particles suspended in some liquid or gas that are like atoms but larger and more controllable. One team at the University of Colorado, Boulder has unveiled its own such particles that they can control with ambient light. They’re useful not only for getting a better understanding of atoms themselves but also for potentially creating larger structures out of these individual units.
“You could make an analogy between these particles and an atom, but the advantage of this system is that it’s in the range of microns,” Ye Yuan, postdoctoral researcher at the University of Colorado, Boulder, told Gizmodo. “So you can observe them with a regular optical microscope.”
These giant “atoms” are flat hexagons made from silica coated with a light-sensitive dye made from the chemical azobenzene. Each hexagon is a bit smaller in width than the finest human hair. They exist in a “liquid crystal,” with liquid crystal being a fancy name for a liquid of rod-shaped molecules in which all of the rods are oriented in the same direction. The rods adjust their orientation around the hexagons, and the interaction between the rods and hexagons governs the rules of this strange realm. The researchers sandwiched the setup between glass plates so they could observe it under a microscope, customized so they could shine specially tuned light onto the sample.
The world of these near-macroscopic atoms was like a warped version of our own reality. Introducing light to these rods and particles causes the system to behave like atoms that are struck by an energy source, moving from a ground to an excited state. This realm also has a concept of charge, just like real-world atoms—but unlike in the real world, like charges attracted while opposite charges repelled in the experiment. The researchers were able to switch the charges by changing the light.
What do you do with a system of tiny, controllable shapes? Yuan explained to Gizmodo that perhaps they could find a use in medicine, carrying and delivering drug molecules to targeted cells. They could lend further insight into “active matter,” systems scientists don’t know much about in which all of the constituent parts move under the influence of consumed energy and begin to exhibit collective behavior, like a flock of birds. They might also find uses in sensors or displays.
One researcher not involved in the study, NYU chemistry professor Stefano Sacanna, told Gizmodo that this system was exciting because the particles responded to ambient light (meaning, not laser beams), which is a weak, easy-to-control field, instead of something difficult-to-control like a magnetic field.
This system, described in a paper published in the journal Nature, certainly isn’t ready for the big time. For starters, it’s two-dimensional, Sacanna said. But, “Controlling the assembly of particles with light could lead to new micro-fabrication technologies,” he told Gizmodo in an email. “Imagine microscopic LEGO bricks that spontaneously assemble into a larger architecture when illuminated by light.”
Ultimately, Yuan told Gizmodo, they’re still trying to figure out what they can do with a system like this.