In the United States alone, 17,000 people await liver transplants. Sangeeta Bhatia’s solution? Engineer a liver from scratch, using photopatterning techniques borrowed from the microchip industry. A completely functional artificial liver requires different types of cells arranged in complex patterns. The University of California, San Diego, associate professor of bioengineering and associate adjunct professor of medicine starts by mixing one type of liver cell with a liquid polymer and covering the mixture with a template. When ultraviolet light shines through the template, illuminated cells get trapped in the polymer; shaded cells can be washed away. By applying different templates and cell mixtures, Bhatia builds up layers that simulate the liver’s natural structure. Human trials remain years away, but meanwhile biotech firm Surface Logix is adapting her liver-cell work for drug research.