Solid state pH and chloride sensor with microfluidic reference electrode

Batch microfabrication and testing of a novel silicon-base miniaturized reference electrode with an ion-exchanging nanochannel array for nitrite determination

“…Compared with a traditional glass tube RE, the nanochannel array of the novel RE can signicantly decrease the loss of chloride ions in the KCl solution and effectively increase the service life of the RE. This shows that the dri rate of a RE reference potential is proportional to the diameter of the ion exchange channel, as obtained by Zevenbergen et al 23 The Ag/AgCl electrode with a thickness of about 0.5 mm was fabricated on a Pyrex 7740 glass using a silver sputtering li-off process and electrochemical treatment using a HCl solution. A hole with a 1.4 mm diameter was prepared using a laser for injecting a saturated KCl solution.…”

“…A typical glass tube RE uses a semipermeable membrane to exchange the internal solution with the external water environment. Previous studies have used high-density microporous polyethylene 22 with a single micron hole 23 instead of the semipermeable membrane of the traditional glass tube Ag/AgCl electrode. This study gradually improved the performance of the electrode, especially the life of the electrode.…”

“…The stability and consistency of the batch-microfabricated miniaturized Ag/AgCl RE were compared with previously reported Ag/AgCl REs 17,18,23,26 and were given in Table 2.…”

“…The lifetime of an electrode is still a severe problem; therefore, studies on the salt bridge of REs have continued. 22,23 Pedrotti et al designed a high-density microporous polyethylene for a restricted ow junction between the internal and external electrolytes. The more favorable characteristics of a microporous membrane for the fabrication of miniaturized junctions are evident in a commercial Vycor membrane.…”

“…When the hole diameter was 20 mm, the potential change was 0.01 mV per day during the testing for two months. 23 In addition, some special applications and integration studies on Ag/AgCl REs have been reported. [24][25][26] Hayashi et al invented a RE to use in a ow-type measuring apparatus by incorporating an immobilized enzyme WE.…”