Blood cell separation is an essential pre-processing step for downstream application such as biochemical analysis, disease diagnosis and therapeutics. Hence, blood cell separation offers a myriad of clinical opportunities. Conventional methods of separation through density gradient centrifugation, and detection using Coulter Counters or antigen-binding (ELISA) present problems in terms of their separation efficiency, accuracy, price, as well as portability of use. In addition, large sample volumes and long processing times might be required to obtain useful results. In this regard, microfluidics presents itself as a viable alternative for blood processing, what with its vast number of merits – low Reynolds numbers laminar flows with ease of control, small sample sizes, biomimetic capability, ease and affordability of fabrication, integration with micro total analysis systems (μTAS), and a small device footprint allowing for easy parallelisation to increase throughput. Numerous methods have been developed over the last few decades, and these can be broadly dichotomised as active or passive methods, the former requiring the application of external force fields for highly precise and complex force modalities. Passive methods, on the other hand, enjoy the benefit of simplicity by eliminating the need for complex device configurations to generate the external fields; most rely mainly on geometric features or unique fluid properties to induce hydrodynamic manipulation of particles.