Digital microfluidic biochips are reforming many areas of biochemistry, biomedical sciences, as well as microelectronics. It is renowned as lab-on-a-chip for its appreciation as a substitute for laboratory experiments. Nowadays, for emergency purposes and to ensure cost efficacy, multiple assay operations are essential to be carried out simultaneously. In this context, parallelism is of utmost importance in designing biochip while the size of a chip is a constraint. Hence, the objective of this study is to enhance the performance of a chip in terms of its throughput, electrode utilisation, and pin count as well. Here, the authors have considered some of the most familiar assay requirements where a sample is to be analysed using different reagents, and identify some parameter(s) of the sample(s) under consideration. Moreover, sample preparation is a vital task in digital microfluidic biochip; thus, dilution of different samples up to different concentrations using buffer (neutral) fluid is a crucial issue. In this design, the authors effectively perform this task in parallel in a number of sub-regions of a given restricted sized chip using an array based partitioning pin-assignment technique while taking care of the cross contamination problem. The design has been verified for some significant real life assay examples. © The Institution of Engineering and Technology 2016.