Microfluidic sub-millisecond mixers for the study of chemical reaction kinetics

We present here, a micromachined, high Reynolds number (2,000 - 6,000), sub-millisecond liquid mixer for the study of chemical reaction kinetics. This 1cm x 1cm x 1mm bulk micromachined silicon mixer is capable of initiating and quenching (starting and stopping) chemical reactions in intervals as short as 100 μs. The centimeter sized mixer chip contains two tee mixers connected by one channel which serves as a reaction chamber. Each tee mixer consists of opposing channels where liquids meet head-on and exit into a third channel forming the base of a "T." Our mixer performance was characterized by employing two carefully chosen chemical reactions with reaction time constants of 3 ms and 9 ms along with visualization techniques using dyes and acid-base indicators.