A microfluidic device fully integrated with three pH sensing electrodes and passive mixer for nanoparticle synthesis

We have proposed a novel microfluidic device for nanoparticle synthesis which is integrated with a pH sensing electrode array for in situ real time pH monitoring and a passive mixer for effective reaction of two chemical fluids within a small scaled microfluidic device. The passive mixer is fabricated with three glass substrates and the mixing channel is designed 3 dimensionally to maximize the mixing efficiency. Moreover, our pH sensing is achieved with three electrodes measurement method. The three electrodes are working electrode of IrO2, counter electrode of Pt and reference electrode of Ag/AgCl, which are fabricated by lift-off process on a silicon substrate. By the anodic bonding of the Si substrate having pH sensing electrode array to the glass substrates having passive mixer, we have accomplished the microfluidic device fabrication. The liquid junction between the flow channel and KCl solution chamber for reference electrode is realized by pores created at both sides of dummy metal layer of Pt during the anodic bonding process. We have performed pH measurement and mixing experiment as well. As a result, we have verified the performance of our microfluidic device.