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Micromachined pH Sensor Using Open Well Structures  

Kim, Heung-Rak (Research Institute of Industrial Science & Technololgy, Process Automation Research Center, Sensor & Instrumentation Team)
Kim, Young-Deog (Research Institute of Industrial Science & Technololgy, Process Automation Research Center, Sensor & Instrumentation Team)
Jeong, Woo-Cheol (Research Institute of Industrial Science & Technololgy, Process Automation Research Center, Sensor & Instrumentation Team)
Kim, Kwang-Il (Research Institute of Industrial Science & Technololgy, Process Automation Research Center, Sensor & Instrumentation Team)
Kim, Dong-Su (Research Institute of Industrial Science & Technololgy, Process Automation Research Center, Sensor & Instrumentation Team)
Publication Information
Journal of the Korean Society for Nondestructive Testing / v.22, no.4, 2002 , pp. 347-353 More about this Journal
Abstract
A structure of a glass electrode-type pH sensor for measuring any concentration of $H^+$ in an aqueous solution was embodied with bulk micromachining technology. Two open well structures were formed, and a reference electrode was secured by the Ag/AgCl thin film in the sloped side of the etched structure. A sensitive membrane of an indicator electrode for generating a potential by an exchange reaction to $H^+$ was made with a glass containing Na 20% or more finely so that its thickness might be $100{\mu}m$ or so, and then it was bonded to one pyramidal structure. A liquid junction for a current path was formed by filling an agar in the anisotropically etched part of the Si wafer, which had a size of $50{\mu}m{\times}50{\mu}m$, and then bonded it to the other. After complete fabrication of each part, it was filled with a 2M KCl reference solution and encapsulated the sensor structure with a cold expoxy. The potential value of fabricated pH sensor was about 90mV/pH in the standard pH solutions.
Keywords
bulk micromachining; anisotropic etching; Ag/AgCl reference electrode; liquid junction; agar; pH meter;
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