Digital Microfluidic Biochip (DMFB) is revolutionizing many areas of Microelectronics, Biochemistry, and Biomedical sciences. It is also known as ‘Labon- a-Chip’ for its popularity as an alternative for laboratory experiments. The mixing of samples and reagents for a biological or chemical lab-on-a-chip is important, yet difficult, in microfluidic operations. As volume is of the order of subnanoliter, the mixing of liquids is hindered by laminar flow conditions. The fixed geometric parameters of the mixer and the type of movement of the coalesced droplet control droplet mixing time. In this paper, we study the effects of varying mixer sizes and propose of mixing strategies applicable to some Polymerase Chain Reaction (PCR) where a series of mixing is required. A design of mixer has been proposed including its pin assignment where reduction of time of mixing is a key challenging issue to enhance the performance of the chip in terms of throughput. © Springer India 2015.