In some embodiments, a chip is used for isolating RBC from a whole blood and includes an accommodating space, a porous membrane and a microchannel system. The accommodating space is used for containing a whole blood sample including RBC debris. The porous membrane is disposed at a bottom of the accommodating space and includes a plurality of pores. A diameter of the pores is larger than a size of the RBC debris and larger than a mean diameter of WBC and CTC. The microchannel system includes a liquid inlet, a liquid outlet and a microchannel. The microchannel is disposed between and communicates with the liquid inlet and the liquid outlet. The microchannel is disposed under the porous membrane. The RBC debris enters the microchannel by penetrating through the porous membrane. |