3D silicon shapes self-assemble with drop of water!

In what could pave the way for tools to deliver drugs to targeted areas of the body or even perform autonomous microsurgery, researchers have devised a way to make silicon, the electronic industry's standard semiconductor material, fold on its own.

Using only a drop of water, scientists have folded flat sheets of silicon nitride into cubes, pyramids, half soccer-ball-shaped bowls and long triangular structures that resemble Toblerone chocolate bars which are almost too tiny to see with the naked eye.

Tiny self-assembling tools could one day deliver drugs to targeted areas of the body or even perform autonomous microsurgery.

"Water is everywhere, is biocompatible, cheap and easy to apply," said Antoine Legrain from University of Twente in the Netherlands.

Using water instead of solder also speeds up the folding of each individual structure.

The so-called solder assembly used the surface tension of melting solder to fold silicon into 3D shapes that more efficiently filled a small space with electrical components.

"If the water-based process is further developed to fold multiple structures at once, it could become cheaper than current self-folding approaches," Legrain said.

To create their menagerie of 3D shapes, the researchers used a custom software programme to first design the flat starting pattern.

They then "printed" the design onto silicon wafers.

To fold the designs, the researchers pumped a small amount of water through a channel they had left in the silicon wafer.

The final structures, which are about the size of a grain of sand, can be opened and closed up to 60 times without signs of wear, as long as they remain wet.

The paper describing the water-based folding system appeared in the Journal of Applied Physics.