Here we demonstrate a new method for droplet fusion based on a surface energy pattern on the walls of a microfluidic device, that does not require active elements nor accurate synchronization of the droplets.

Fully integrated: Mass spectrometry has been integrated into a detection scheme for microdroplets that are created within microfluidic channels (see picture, scale bar 200 microm). This technique allows droplets to be identified based on the compounds they contain, and combines fluorescence screening with MS analysis. These experiments indicate how similar approaches can be applied to the ambitious goals of on-chip protein evolution and chemical synthesis.

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.

Specific-purpose microfluidic devices have had considerable impact on the biological and chemical sciences, yet their use has largely remained limited to specialized laboratories. Here we present a general-purpose software-programmable microfluidic device which is capable of performing a multitude of low-and high-level functions without requiring any hardware modifications. To demonstrate the applicability and modularity of the device we implemented a variety of applications such as a microfluidic display, fluid metering and active mixing, surface immunoassays, and cell culture. We believe that analogously to personal computers, programmable, general-purpose devices will increase the accessibility and advance the pervasiveness of microfluidic technology.Microfluidic technology has progressed considerably in the last decade, through the development of simple fabrication methods such as soft lithography, 1 the implementation of micromechanical valves, 2,3 and the development of monolithic integration techniques.4 It is now possible to robustly fabricate microfluidic devices containing thousands of components, enabling the implementation of complex high-throughput assays.5,6 These fluid handling capabilities combined with its considerable economies of scale have made microfluidic technology essential in many areas including cell culture, 7-12 protein biochemistry, 5,13,14 protein crystallization 15,16 and chemistry. 17The developments in microfluidic integration have frequently been compared to the evolution of computer hardware.18 Before the advent of the integrated circuit, the first electronic computers, such as the ENIAC, 19 needed to be physically re-wired before each new computing task. Analogously, 60 years later, in order to apply a microfluidic device to a new task, a new channel layout needs to be designed and physically implemented. This is a long and expensive process that requires expert knowledge of microfabrication and fluid physics.20 The development of programmable, general-purpose computing machines transformed computers into ubiquitous information-processing tools.21 It follows that the development of a fully software-programmable microfluidic device (PMD) could prove equally crucial for microfluidic technology. PMDs would allow the establishment of generic hardware elements whose function could be configured through an additional layer of software abstraction. With a generic architecture users could focus on adapting, developing, and disseminating software tools for their applications.Furthermore, implementing numerous applications in a generic architecture would greatly decrease development costs.Programability and versatility have been successfully achieved in electrowetting-on-dielectric microfluidic devices.22,23 However, integration and miniaturization in these devices is still limited as systems commonly contain only tens of active components and the unit volumes handled often fall in the microlitre range. Nevertheless, electrowetting-on-dielectric microfluidic devices have recently been a...