A printer that prints not with ink but with metal and ceramic is now a reality. Scientists took an ordinary drop of water containing dissolved metal salts and made it deposit copper, zinc oxide, or nickel hydroxide onto a surface — all with precision down to millionths of a meter.

The secret lies in electricity. The droplet hangs on the tip of a thin needle, and a weak current is passed beneath the surface. Metal ions from the solution turn into solid material right at the point of contact. By changing the voltage or the solution composition, a different material starts to grow from the same drop. This way, without lifting the needle, you can "draw" a conductive track and, right next to it, an insulator.

Why does this matter? Modern microchips are made in vacuum chambers, layer by layer, through masks. That's expensive and slow. The new printing works in air, from cheap aqueous solutions, and requires no masks. You can quickly create prototypes of sensors, transistors, microbatteries, and test them right away.

The scientists demonstrated that even three-dimensional structures can be printed this way: for example, pillars of zinc oxide that glow under voltage. In the future, such a printer could assemble entire electronic circuits — layer by layer, material by material, from a single drop.