Low-Cost Dilution Engine for Sample Preparation in Digital Microfluidic Biochips

Recently developed digital microfluidic biochips can implement biochemical laboratory assays (protocols) on a small size chip for automatic and reliable analysis of biochemical fluid samples. Dilution of a sample fluid is the basic step required in almost all bioassays. We propose a dilution engine for sample preparation that can produce multiple (a stream of) droplets of the target fluid with the same concentration level and present a scheduling scheme for mapping the dilution steps into the dilution engine. Our proposed architecture for dilution engine uses one ($1:1$) mix-split microfluidic module (mixer) and a constant number of storage units. Its performance is compared with another layout of only one mixer with no storage unit. Simulation results show that the proposed scheme can efficiently reuse the waste droplets of earlier steps and hence utilizes less amount of expensive biochemical fluids. Moreover, the scheme generates multiple target droplets with the same concentration level in less number of dilution steps (i.e., time) and at a relatively lower cost.