Crystal Construction Sets: Nanobricks That Assemble and Disassemble Themselves express
A handful of lead sulfide nanocrystals coated with charged molecules spontaneously assembles into a perfect crystalline lattice. Each nanocrystal is like a brick just a few nanometers across, while the charged molecules on its surface act as the mortar. In solution, the bricks find each other and stack into a neat wall, where every brick sits exactly in place and even points the same way.
Previously, it was thought that such constructions freeze forever once built. But new work shows the wall can be carefully dismantled back into individual bricks and then reassembled. It's like a building set that isn't glued together permanently but holds thanks to many weak contacts. The charged mediator molecules, like tiny magnets, pull particles toward each other without letting them fuse for good.
Such materials can be reconfigured for different tasks. Assemble the lattice one way, you get one set of properties; take it apart and reassemble differently, you get another. This opens the door to electronics that change their characteristics on command, just as a building set transforms from a car into a plane.
A lead sulfide nanocrystal 5 nanometers across is about 20 times smaller than an influenza virus. If you scaled it up to the size of a brick, an ordinary brick would become as tall as a nine-story building.