3D printing on the micrometer scale

Three-dimensional printers are popping up everywhere these days. Some are small enough to fit in a briefcase and others are large enough to build print houses, but scientists at the Vienna University of Technology are going for the microscopic. Earlier this year, the university built a 3D printer that uses lasers to operate on a tiny small scale. Now they’re refining the technique to enable precise placement a selected molecule in a three-dimensional material. This process, called “3D-photografting,” can potentially be used to create a “lab on a chip” or artificially grow living tissue.
Developed by material sciences specialist Prof. Jürgen Stampfl macromolecular chemist Prof. Robert Liska, the 3D-photografting technique is based on a sort of super sponge called hydrogel. This is a network of polymer chains that trap water much in the way that proteins in cooked egg whites do. Hydrogels are over 99 percent water and some varieties look like little transparent blobs.
Hydrogels not only trap water, but any other molecules that scientists wish to introduce. If the polymers that make up the hydrogel can be made to coagulate under precise control, they can form a scaffolding for molecules and even living cells.
In the Vienna University of Technology 3D-photografting technique, molecules are placed in inside the hydrogel. Then, at the points where the scientists wish to fix a molecule, a laser is focused using a special four-micron lens. Only at that point of focus will the laser be strong enough to break the polymer’s bonds photochemically. This leaves a very reactive spot where the molecule can bond. As the laser moves along, it forms a matrix out of the hydrogel to which can be attached chemical signals, cells or fluorescent molecules.