The present invention provides a device for isolating target biomolecules or cells from samples, particularly biological samples. In particular, the device comprises a loading mixture, which contains the biological sample and a first binding entity that specifically binds to the target biomolecule or target cell; and a micro-channel coated with a second binding entity that binds directly or indirectly to the first binding entity. Methods of capturing, detecting, and/or evaluating target biomolecules or target cells (e.g. cancer cells) in biological samples are also disclosed.