The processes separation and focusing of microparticles in microfluidic devices have developed to be an essential part of several applications in biomedical, clinical, chemical, environmental and engineering domains. Regarding their part in the diagnosis and treatment of diseases, such as cancer, particle separation processes play an important role as they bring about earlier diagnosis beyond the one provided by customary medical and clinical treatment. Metastatic cancer, for instance, has long been under study and research, with the aim to find the best way to detect and cure such disease. Microfluidics offer a relatively efficient technique in particle separation. The presence and frequency of circulating tumor cells (CTCs) in blood are critical in the course of early detection of cancer. However, such cells are rare and infrequent, which makes it challenging to detect them easily and with precision. In this paper, we illustrate the separation of particles in a spiral microchannel based on inertial forces and differential migration. This passive microfluidic device can deliver the separation of particles based on their sizes. It’s made of four loops with an initial radius of curvature of 2 cm, a channel width of 500 μm, and a height of 50 μm. Systematic analysis, the manufacturing process, simulations and the methodology of this microfluidic system are presented here alongside the experimentation. The straightforwardness, material and productivity of this design makes it a perfect model for lab-on-a-chip (LOC) or micro total analysis systems (μTAS), as it allows for continuous separation applications.