Thin-film IrOx pH microelectrode for microfluidic-based microsystems

• Published in: Biosensors & bioelectronics Vol. 21; no. 2; pp. 248 - 256
• Main Authors: GES, Igor A, IVANOV, Borislav L, SCHAFFER, David K, LIMA, Eduardo A, WERDICH, Andreas A, BAUDENBACHER, Franz J
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier Science 15-08-2005
• Subjects: Animals; Biological and medical sciences; Biosensors; Biotechnology; Cell Culture Techniques - instrumentation; Cell Culture Techniques - methods; Cells, Cultured; CHO Cells; Cricetinae; Cricetulus; Equipment Design; Equipment Failure Analysis; Fibroblasts - chemistry; Fundamental and applied biological sciences. Psychology; Humans; Hydrogen-Ion Concentration; Ion-Selective Electrodes; Iridium - analysis; Iridium - chemistry; Membranes, Artificial; Methods. Procedures. Technologies; Microelectrodes; Microfluidic Analytical Techniques - instrumentation; Microfluidic Analytical Techniques - methods; Miniaturization; Various methods and equipments; Acidification; Oxides; Indium; pH sensor; Thin film; Electrochemical deposition; Detector; Microequipment; Electrochemistry; Microelectrode; pH; Cell acidification rate; Indium oxide films; Miniaturization; Microfluidics; Microfluidic device
• ISSN: 0956-5663; 1873-4235
• DOI: 10.1016/j.bios.2004.09.021

Microsensors are valuable tools to monitor cell metabolism in cell culture volumes. The present research describes the fabrication and characterization of on-chip thin-film iridium oxide pH microsensors with dimensions of 20 microm x 20 microm and 20 microm x 40 microm suitable to be incorporated into nl volumes. IrOx thin films were formed on platinum microelectrodes by electrochemical deposition in galvanostatic mode. Anodically grown iridium oxide films showed a near super-Nernstian response with a slope of -77.6+/-2 mV/pH at 22 degrees C, and linear responses within the pH range of 4-11. Freshly deposited electrodes showed response times as low as 6s. Long-term studies showed a baseline drift of 2-3 mV/month, which could easily be compensated by calibration. This work demonstrated for the first time the use of planar IrOx pH microelectrodes to measure the acidification rate of CHO and fibroblast cells in an on chip cell culture volume of 25 nl with microfluidic control.