In this research, we aimed to develop a new type of core-shell electrospun fiber, possessing “short” length (core) and “concentrated” polymer brush (shell). We prepared electrospun fibers with initiating moiety for surface-initiated atom transfer radical polymerization (SI-ATRP), one of living radical polymerizations. Then we grafted poly(sodium styrene sulfonate) (PSSNa) on the fibers by SI-ATRP. After the polymerization, we mechanically cut the electrospun fibers with a homogenizer, yielding regulated shortened fibers. Our ultimate goal is to make a novel shortened nanofibril biomaterial with concentrated brush as cell growth scaffolds. Therefore we expect that this unprecedented short nanofiber can be broadly applied as a biomaterial owing to the unique structures and properties of the concentrated brush. The details will be discussed.