This investigation presents two methods for multiplexed droplet generation in digital microfluidic devices. Analytical and experimental results show that the number of electrical output signals required for multiple reagent systems can be reduced by electrically connecting all but one electrode in each droplet generation path on the device. Both methods reduce the number of electrical signals required for generating droplets from multiple reservoirs by M(N-1), where M is the number of manipulation electrodes in the generation path and N is the number of reservoirs on the device. The first method uses individually controlled reservoirs to minimize the manipulation of the fluid in the unused reservoir, while the second method individually controls one of the electrodes in the generation pathway to allow for closed loop control of droplet generation. In both cases, droplets are kept at rest by simultaneously activating or deactivating all adjacent electrodes. These methods can be easily integrated into devices with multiple reservoirs without computational expense or prior knowledge of the electrode activation sequence. They can also be used in concert with droplet control algorithms for pin constrained systems to further reduce the number of output channels required in a digital microfluidic device.
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