Abstract: The present invention relates to a gradient-on-a-chip device for quantification of cell migration and metastatic potential of tumor cells. The device comprises a chip having a chip surface, and a nano gradient layer of nanoparticles provided on the chip surface. The nano gradient layer having a gradient direction along an axis of an X-Y plane of the chip surface. The device further comprises a biomolecule conjugated to the nanoparticles and a linker conjugated to the nanoparticles, the linker linking together said biomolecule to said nanoparticles. The chip surface has at least one guiding structure arranged to guide the tumor cells in the gradient direction, the guiding structure extending in the gradient direction and delineating a migration corridor comprising the nano gradient layer.