Intergrated micro-liquid dosing system

A new concept for micro-mixing of liquid is introduced and feasibility is demonstrated. The mixer allows fast mixing of small amounts of two liquids and it is application to micro-liquid handling systems [1]. The mixer has a channel for the liquid, an inlet port for the reagent, and a 2.2 mm × 2 mm × 330 μm mixing area, and its bottom has 400 micro-nozzles (15 μm × 15 μm). Through these nozzles, a reagent is injected into the sample liquid, making many micro-plumes. These plumes increase the contact surface between the two liquids drastically, and hasten the speed of the mixing by diffusion. The nozzle holes and channel are etched using KOH into a 3-inch (100)-Si wafer from both sides. The fabrication process is extremely simple. Flow visualization by microscope shows the mixing is complete within a few seconds, and absorptiometry using a pair of optical fibers showed that a homogeneous state of mixing is reached in 1.2 seconds, when the total volume injected is 0.5 μl and the injection flow rate is 0.75 μVs