US Patent 8377685 Microfluidic device having stable static gradient for analyzing chemotaxis

A microfluidic method and device for testing and analyzing chemotaxis by providing a stable, static fluid gradient. The device includes a sink reservoir for receiving biological cellular material and a source reservoir for receiving a chemoattractant. The biological cellular material migrates through a low fluid volume microfluidic gradient channel located between the source and sink reservoirs. The fluid in the gradient channel is static and stable due to a high fluid volume closed circuit bypass microfluidic channel also in fluid communication with the source and sink reservoirs, whereby the bypass channel relieves any pressure differential imparted across the gradient channel.