Microfabricated diffusion-based chemical sensor

A channel cell system for detecting the presence of analyte particles in a sample stream also comprising larger particles comprising:

• a) a laminar flow channel;
• b) at least two inlet means in fluid connection with said laminar flow channel for respectively conducting into said laminar flow channel (1) an indicator stream and (2) said sample stream;
• c) wherein said laminar flow channel has a depth sufficiently small to allow laminar flow of said streams and a length sufficient to allow particles of said analyte to diffuse into said indicator stream to the substantial exclusion of said larger particles in said sample stream to form a detection area;
• d) outlet means for conducting said streams out of said laminar flow channel to form a single mixed stream.

A system for detecting the presence of particles of an analyte in a liquid sample stream also comprising larger particles, said system comprising a channel cell fabricated by etching channel grooves in the form of a "T" or a "Y" having a central trunk and two branches into the surface of a silicon microchip and covering said grooves with glass, said channel cell comprising:

• a) a laminar flow channel formed of the trunk of said "T" or "Y";
• b) two inlet means comprising branches of said "T" or "Y" in fluid connection with said laminar flow channel for respectively conducting into said laminar flow channel (1) an indicator stream comprising an indicator substance which indicates the presence of said analyte particles by a detectable change in property when contacted with said analyte particles, and (2) said sample stream;
• c) wherein said laminar flow channel has a depth sufficiently small such that parallel laminar flow of said streams occurs therein, and a length sufficient that particles of said analyte diffuse into said indicator stream to the substantial exclusion of said larger particles in said sample stream to form a detection area, and said indicator and sample streams reach equilibrium within said laminar flow channel;
• d) outlet means for conducting said streams out of said laminar flow channel to form a single mixed stream.