Microdroplets have great potential for high-throughput biochemical screening. We report the design of an integrated microfluidic device for droplet formation, incubation and screening. Picolitre water-in-oil droplets can be stored in a reservoir that contains approximately 10(6) droplets. In this reservoir droplets are stable for at least 6 h, which gives an extended timescale for biochemical experiments. We demonstrate the utility of the system by following the in vitro expression of green fluorescent protein. The high efficiency allows protein expression from a single molecule of DNA template, creating "monoclonal droplets" in which genotype and phenotype are combined in one emulsion compartment.

The nanotechnology revolution of the past decade owes much to the science of lithography, an umbrella term which encompasses everything from conventional photolithography to “unconventional” soft lithography and the self‐assembly of block polymers. In this review, some of the recent advances in lithography are summarized with special reference to the microelectronics industry. The next generation photolithography, two‐photon lithography, step‐and‐flash imprint lithography and nanofabrication using block copolymers are covered, in an attempt to describe more recent work in this vibrant and active field of research. Copyright © 2006 John Wiley & Sons, Ltd.

We describe the development of an enzyme assay inside picoliter microdroplets. The enzyme alkaline phosphatase is expressed in Escherichia coli cells and presented in the periplasm. Droplets act as discrete reactors which retain and localize any reaction product. The catalytic turnover of the substrate is measured in individual droplets by monitoring the fluorescence at several time points within the device and exhibits kinetic behavior similar to that observed in bulk solution. Studies on wild type and a mutant enzyme successfully demonstrated the feasibility of using microfluidic droplets to provide time-resolved kinetic measurements.

The contents of microdroplets can be extracted on‐chip and incorporated by electrocoalescence into a continuous microfluidic stream. Individual droplets can be selected based on their contents. As a proof of principle, a fluorescence detection system was used to collect droplets containing low levels of a fluorescent dye (see picture of droplets passing through the device) as well as single fluorescent beads.