Sometimes, science follows science fiction. Take, for example, the case of "living crystals," which sounds like a race of alien beings. But thanks to science, they're now real.
Physicists Jérémie Palacci and Paul Chaikin of New York University had created microscopic cubes of hematite - a compound consisting of iron and oxygen, sheathed in a spherical polymer coat with one corner exposed - that behave as if they were alive.
Under certain wavelengths of blue light, hematite conducts electricity. When the particles are placed in a hydrogen peroxide bath under blue light, chemical reactions catalyze around the exposed tips.
As the hydrogen peroxide breaks down, concentration gradients form. The particles travel down these, aggregating into crystals that also follow the gradients.
Random forces pull the crystals apart, but eventually they merge again. The process repeats again and again, stopping only when the lights go out.
The ultimate goal of the work is to study how complicated collective behaviors arise from simple individual properties, perhaps informing molecular self-assembly projects, but it’s hard not to think about the origin-of-life implications.
“Here we show that with a simple, synthetic active system, we can reproduce some features of living systems,” Palacci said. “I do not think this makes our systems alive, but it stresses the fact that the limit between the two is somewhat arbitrary.”
Chaikin notes that life is difficult to define, but can be said to possess metabolism, mobility, and the ability to self-replicate. His crystals have the first two, but not the last.
I, for one, welcome our new crystal overlords!
Brandon Keim of Wired has the story and video clip: Link