Printer writes micro 3D objects

Existing three-dimensional printers, which build up objects from layers of melted metal powder, melted plastic powder or quick-drying ink-jet ink, print relatively slowly because it takes time for each layer to dry. And like that of their two-dimensional counterparts, the print resolution, or feature size, is limited by the granular nature of these processes.

University of Illinois researchers have come up with a new type of quick-setting three-dimensional ink that works a bit like a microscopic tube of toothpaste. The researchers' printer robotically deposits a continuous, elastic-like ink filament into a liquid rather than putting ink drops onto a surface.

The filament hardens in the liquid rapidly enough to allow for printing three-dimensional structures that have features like unsupported spanning elements. The process yields complete three-dimensional structures in about five minutes, and provides resolutions that are close to two orders of magnitude finer than existing methods, according to the researchers. The researchers' prototype has nozzles that vary in diameter from five microns to 0.5 microns. A micron is one thousandth of a millimeter.

Because the resolution is so high, the process has the potential to produce templates for structured materials, like photonic band gap materials used to control light, microfluidic devices used for biological and chemical testing, and bioscaffolds for tissue engineering.

The researchers are currently refining inks for structures made from refractive-index materials like selenium and bioactive materials.

The method could be used in photonic bandgap and tissue engineering applications in two to five years, according to the researchers. The work appeared in the March 25, 2004 issue of Nature.