Ben P. Stein in Phys.Org:
Researchers at the National Institute of Standards and Technology (NIST) have developed a new method of 3-D-printing gels and other soft materials. Published in a new paper, it has the potential to create complex structures with nanometer-scale precision. Because many gels are compatible with living cells, the new method could jump-start the production of soft tiny medical devices such as drug delivery systems or flexible electrodes that can be inserted into the human body.
A standard 3-D printer makes solid structures by creating sheets of material—typically plastic or rubber—and building them up layer by layer, like a lasagna, until the entire object is created. Using a 3-D printer to fabricate an object made of gel is a “bit more of a delicate cooking process,” said NIST researcher Andrei Kolmakov. In the standard method, the 3-D printer chamber is filled with a soup of long-chain polymers—long groups of molecules bonded together—dissolved in water. Then “spices” are added—special molecules that are sensitive to light. When light from the 3-D printer activates those special molecules, they stitch together the chains of polymers so that they form a fluffy weblike structure. This scaffolding, still surrounded by liquid water, is the gel. Typically, modern 3-D gel printers have used ultraviolet or visible laser light to initiate formation of the gel scaffolding. However, Kolmakov and his colleagues have focused their attention on a different 3-D-printing technique to fabricate gels, using beams of electrons or X-rays.
More here.