Effect of Volumetric Split-Errors on Reactant-Concentration During Sample Preparation with Microfluidic Biochips

Recent microfluidic technologies offer suitable platforms for automating sample preparation on-chip, and typically on a digital microfluidic biochip, a sequence of (1 : 1) mix-split operations is performed on fluid droplets to achieve the target concentration factor of a sample. A (1 : 1) mixing model ideally mixes two unit-volume droplets followed by a (balanced) splitting into two unit-volume daughter-droplets. However, a major source of error in fluidic operations is due to unbalanced splitting, where two unequal-volume droplets are produced. Such volumetric split-errors occurring in different mix-split steps of the reaction path often cause a significant drift in the target-CF, the precision of which cannot be compromised in life-critical assays. In order to circumvent this problem, several error-recovery techniques have been proposed recently for DMFBs. Unfortunately, the impact of such fluidic errors on a target-CF and the dynamics of their behavior are not yet fully understood. In this work, we investigate the effect of multiple volumetric split-errors on various target-CFs during sample preparation. We also perform a detailed analysis of the worst-case scenario, i.e., when the error in a target-CF is maximized. This analysis may lead to the development of new techniques for error-tolerant sample preparation with DMFBs without using any sensing operation.