Fig. 4From: Microfluidic devices for neutrophil chemotaxis studiesThe device configuration of the membrane-based concentration gradient generator. The solid arrows denoted fluidic path, and the dotted arrows denoted diffusion paths. The concentration gradient in the gradient forming channel was controlled to be stable by the running sample and buffer solutions in the respective overlaying channels. Reprinted from Ref. [38], Copyright (2013), with permission from ElsevierBack to article page