Scientists from the University of Twente in the Netherlands have discovered a technique to facilitate the self-assembly of silicone nitride sheets on the microscopic level by introducing tiny droplets of water that cause the flat prefabricated formations to fold into several different three dimensional structures.
A similar technique dates back to the 1990s when silicon was folded into 3-D shapes using the surface tension of melting solder. This helped decrease the size of semiconductors and increase the efficiency of the placement of electrical components on smaller surface areas. This method has since been replaced by a photolithographic printing process by companies like Intel and AMD.
Recently, researchers found that water is a sufficient catalyst for this nano origami technique, which is also faster than the solder used decades before. Although this is not the first time the method has been attempted, the discovery that the precise placement of the water droplet is key to its success offers a breakthrough.
Using a custom software program, scientists start with a flat 3-D design that is printed onto silicon wafers. Then, hinges are carved out of the surface of the material, allowing the self-assembly to occur. The folding takes place when a small drop of water is applied to the flat sheet. The applied water molecules stick to the surface of the silicone, pulling the hinged sections together to form the desired shape. As long as they remain wet, the tiny sand-sized structures can maintain their shape or expand and contract up to 60 times without signs of wear.
The means to unfold and refold structures in this way could be useful in many medical applications. Eventually, this technology could lead to novel methods for micro-biopsies or accurate drug delivery systems implemented into advanced healthcare procedures.