The subject matter described herein relates to devices and methods for capturing micrometer scale objects from a fluid flow, and more particularly, to devices and methods for capturing cells. The devices generally comprise an array of posts configured and arranged to selectively direct the micrometer scale objects toward trapping channels defined between posts in which the micrometer scale objects can be trapped, and to direct smaller particles through bypass channels around the posts. Methods for using the devices to trap cells, analyze cells and treat cancer are also described.