A new way to build microscale pipes in three dimensions boosts the sophistication of chips that manipulate fluids to perform chemical reactions, biomedical tests, and other tasks, its developers say.
A drawback of most microfluidic chips is that their pipes often intersect because they're all on one level. So valves must control fluid flows, notes Emil P. Kartalov of the University of Southern California in Los Angeles.
In one established method for making such single-layer chips, a chip builder coats a mold with a thick layer of liquid polymer called polydimethylsiloxane, or PDMS. Ridges in the mold form voids in the polymer that serve as channels f