Via ScienceDaily: researchers "are applying new techniques and materials to come up with artificial blood vessels [that] will be able to supply necessary nutrients to artificial tissue and maybe even complex organs in the future. ... It seemed practically impossible to build structures such as capillary vessels that are so small and complex, especially the branches and spaces in between. But production engineering came to the rescue because rapid prototyping makes it possible to build workpieces specifically according to any complex 3-D model. Now, scientists [are] working on transferring this technology to the generation of tiny biomaterial structures by combining two different techniques: the 3-D printing technology established in rapid prototyping and multiphoton polymerization developed in polymer science ... A 3-D inkjet printer can generate 3-dimensional solids from a wide variety of materials very quickly. It applies the material in layers of defined shape and these layers are chemically bonded by UV radiation. This already creates microstructures, but 3-D printing technology is still too imprecise for the fine structures of capillary vessels. This is why these researchers combine this technology with two-photon polymerization. Brief but intensive laser impulses impact the material and stimulate the molecules in a very small focus point so that crosslinking of the molecules occurs. The material becomes an elastic solid, due to the properties of the precursor molecules that have been adjusted by the chemists in the project team. In this way highly precise, elastic structures are built according to a 3-dimensional building plan."