
Cover image: Microfluidic formulator device. Fluidic logic and precision metering elements allow for arbitrary chemical mixtures to be generated within a 5-nl mixing ring (center). The flexibility and precision of this device allow for the automated combinatorial mixing of a set of stock solutions with a precious sample. The device is used to map out protein solubility behavior for the rational design of crystallization experiments. See the article by Hansen et al. on pages 14431–14436. Photograph courtesy of Carl Hansen.