Automatic on-chip sequential processing for bio-microsystems

As a trial to realize an automatic microfluidic system, functions such as automatic valve operation, adjustment of mixing time, pH-regulation, and sensing were integrated on a chip. Microfluidic transport was achieved by capillary action. The transport and merge of solutions was controlled by gold working electrodes that functioned as valves. The mixing valve was also used as a delay line to take enough time for mixing. The pH of the mixed solution could be adjusted using an electrochemical pH-regulator, and gaseous ammonia produced from the solution could be measured using an air-gap ammonia sensor. The function of the entire system was checked in the enzymatic reaction of urea.