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3-D printing on the micrometer scale


September 2, 2012

Fluorescent 3D pattern 180 µm wide (Image: Vienna University of Technology)

Fluorescent 3D pattern 180 µm wide (Image: Vienna University of Technology)

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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.

Being able to create a microscopic 3D matrix is a big leap forward for true bioengineering. The matrix can act as a scaffold for positioning cells by means of chemical markers telling them where to grow - much in the way that the extracellular matrix in living tissue does. In this way, complicated structures such as capillaries can be “printed.”

The Vienna University scientists see the process as having wide applications from biology to microengineering chemical sensors, but there may come a day when a surgeon in search of a kidney for transplantation may need go no further than pressing the print button.

Source: Vienna University of Technology

About the Author
David Szondy David Szondy is a freelance writer based in Monroe, Washington. An award-winning playwright, he has contributed to Charged and iQ magazine and is the author of the website Tales of Future Past. All articles by David Szondy
1 Comment

The smallest 3D structures are on the order of a few atoms and have been around for more then 30 years. For the last 15 years we have been able to make such tiny structures in hardest materials known to man like tungsten and silicon carbide. This latter work was done here in the States.

Although David doesn't quite understand the "3D Technology" he is describing, some of us do.

The key point about this is the hydrogel structure into which the scientists can introduce various (water soluble) materials. These materials are as small a molecule as they can be and that does not actually matter because the system limit is established by the classical limit of focusing the LASER to a spot or volume element. Giving the system created the benefit of the doubt this is a voxel (volume element) about 4 microns cubed.

Inside this 4 micron voxel there could one or 100,000 molecules (this voxel is the volume of human cell). This is the limit of resolution not the molecule- the molecule is the paint used to paint the voxel.

To make smaller voxels the hydrogel must get thinner and thinner- but this defeats the whole point of the work the scientists are doing.

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