High-throughput dilution engine for sample preparation on digital microfluidic biochips

The new generation of digital microfluidic biochips is capable of implementing complex biochemical laboratory assays (bioprotocols) on a tiny device for automatic and reliable analysis of fluid samples. Dilution of a sample fluid is one of the basic steps required in almost all bioprotocols. The authors design a dilution engine for sample preparation that can produce a stream of target droplets with a desired concentration factor by reusing the waste droplets. Also, a scheduling scheme is presented for mapping the dilution steps into the dilution engine. Next, an architecture is proposed to implement the dilution engine using only one (1:1) mix-split microfluidic module (mixer). The authors consider two schemes: (i) the base approach, where no on-chip storage unit (additional electrode) is available, and (ii) when a constant number of storage units is provided. Simulation results show that the second scheme saves the expensive reactants most efficiently, produces a stream of target droplets very fast and is highly suitable for supplying the required number of droplets as needed.