Circulating tumor cells(CTCs)are cancer cells that are shed from primary tumors and travel through the bloodstream to other organs.1 CTCs may play a key role in metastasis,which is known to be the direct cause of 90% of cancer deaths.2,3 There is a great demand for a method to help isolate these CTCs from the bloodstream,but one of greatest challenges in CTCs detection is their extreme rarity in the blood.Very few CTCs(1~10 CTCs in 1 mL whole blood)are present in patients with metastatic disease.In order to isolate and analyze this rare cell population,various techniques were developed,including antibody-based surface marker positive selection,and methods that use physical properties of CTCs to negatively exclude background cells from a CTC population.4,5 However,methods to capture cells for functional downstream analyses are limited due to inaccessibility of the captured sample or labeling techniques that may be prohibitive to cell function.In this work,we demonstrate a label-free microfluidic platform for the continuous high throughput(~mL/min)processing of whole blood from cancer patients with efficient isolation of cancer cells using deterministic lateral displacement(DLD)structure.6,7 In this microfluidic platform,we had designed a new low-cost pressure regulating system to circulate the sample.A very small vacuum pump was used for drawing the whole blood samples into sample tubes and a positive pressure regulating system was used for injecting source samples and PBS into the DLD chip at any flow rate.Using this platform,we can isolate the CTCs at 1 mL/min with 95% recovery efficiency,some clinical cancer patient samples were also tested.The advantage of our device is very easy to operate by any doctor for clinical identification of Circulating tumor cells from cancer patients