Sedimentation induced hydrodynamic separation for multi-particles using tapered microfluidic chip

Separation of micro-particles is important in various industries for example food processing, biological analysis, mineral synthesis and environmental [1]. For example, separation of harmful bacteria and unwanted microbes during fermentation process and packaging during food processing [2]. Moreover, the separation of human blood to its components such as red blood cell (RBC) and platelets may help to provide early disease diagnosis related to blood especially blood hereditary problems, blood clotting, anaemia and it can also be used for circulating tumour cells (CTC) detection [3]–[5]. The emergence of microfluidic technology facilitates progress in various developments of separation devices. Microfluidic based separation device offers vast advantages for example it uses less reagents, reduced costs, operates at low power, uses smaller sample volumes, small and portable, flexible and allow for integration with other modules and with minimum operator handling [6]–[9]. Passive separation techniques work using fluid manipulation or particle interaction for example field flow fractionation (FFF) [10]–[12], filtration [13]–[16], hydrodynamic [17]–[19] and sedimentation [20]. It serves as the most fundamental approach and broadly investigated. Microfluidic based hydrodynamic separation manipulates fluid flow and suitable for separation based on size and density. It offers simple design and straightforward operation. In addition, the devices have been tested for separation of both non-biological and biological particles such as microbeads, polymer, colloids, cancer cells and RBC [21]–[24]. Although the techniques have been tested and proven to be efficient, it still suffers from being slow, need for sheath fluid and need for longer channel dimensions [12], [25], [26]. In this chapter, we describe a simple passive separation device for separation of polydisperse samples based on size. The device performs the separation by utilizing hydrodynamic properties of fluid and improves the samples purity through sedimentation effect resultant from the tapered microfluidic design