Dielectrophoresis-based programmable fluidic processors.

Droplet-based programmable processors promise to offer solutions to a wide range of applications in which chemical and biological analysis and/or small-scale synthesis are required, suggesting they will become the microfluidic equivalents of microprocessors by offering off-the-shelf solutions for almost any fluid based analysis or small scale synthesis problem. A general purpose droplet processor should be able to manipulate droplets of different compositions (including those that are electrically conductive or insulating and those of polar or non-polar nature), to control reagent titrations accurately, and to remain free of contamination and carry over on its reaction surfaces. In this article we discuss the application of dielectrophoresis to droplet based processors and demonstrate that it can provide the means for accurately titrating, moving and mixing polar or non-polar droplets whether they are electrically conductive or not. DEP does not require contact with control surfaces and several strategies for minimizing surface contact are presented. As an example of a DEP actuated general purpose droplet processor, we show an embodiment based on a scaleable CMOS architecture that uses DEP manipulation on a 32 x 32 electrode array having built-in control and switching circuitry. Lastly, we demonstrate the concept of a general-purpose programming environment that facilitates droplet software development for any type of droplet processor.