Circulating tumor cells (CTCs) may become a new foundation for early stage cancer diagnosis requiring minimal patient effort [1]. This approach can overcome the limitations of current diagnostic technologies, including computer-aided tomography (CT), magnetic resonance imaging (MRI), X-ray mammography, and ultrasound (UR) which can detect only highly calcified tumors at relatively high cost. Several studies have demonstrated CTC capture using microfluidic devices to identify the presence of human breast cancer, and the CellSearch™ immunomagnetic system (Johnson & Johnson, New Brunswick, NJ) is approved by the Food and Drug Administration (FDA) for monitoring post-treatment therapy, but all of the systems reported have either a long diagnosis time or unacceptable capture rates [2, 3]. CTCs in human peripheral blood are very rare events, typically 1 ∼ 2 CTCs in 1 mL of circulating blood. This low concentration of CTCs requires a large sample volume (∼7.5 mL) to ensure detection. However, current affinity-based microfluidic devices for cell capture usually operate at very low flow rates to increase the capture rate. Therefore, developing high flow rate microfluidic devices for CTC capture is essential and challenging. A new concept of high flow rate device is introduced, simulated, and tested at high flow rates.