Fig. 3

Examples of microgrooves-based devices. A Two-channels microgrooves-based microfluidic device. The two high channels connected by a series of thin microgrooves are loaded with different chemicals to generate gradients in microgrooves. (Figure reproduced from Ref. [32]); B Illustration of the D²-Chip. The gradient channel is connected to the source channel and the sink channel by 3 µm microgrooves defined as the docking structures. The source inlets are loaded with equal volumes of medium with and without chemoattractant, and a stable linear chemoattractant gradient is generated in the middle gradient channel based on the diffusion of the chemoattractant solution and the medium. (Figure reproduced from Ref. [70]); C Schematic diagram of the novel microfluidic competitive chemotaxis-chip(µC³). Healthy neutrophils(blue), super-low dose (1 ng/mL) of LPS (red neutrophil) and high dose (100 ng/mL) of LPS (orange neutrophil) show different migration under the environment with and without chemoattractant gradients. The gradient was formed within the migration channels from the chemoattractant reservoir to the central loading channel and stayed stable for a long time. (Figure reproduced from Ref. [71])