A cobalt-coated needle-type microelectrode array sensor for in situ monitoring of phosphate

In this paper, a new cobalt-coated needle-type microelectrode array sensor for in situ measurements of phosphate has successfully been designed, fabricated and characterized. MEMS technologies were used to fabricate microelectrode arrays with a small tip size. An HF-based etching technique was used to taper and sharpen three-dimensional glass probes. A cobalt thin film was electroplated on a gold conductive layer using a cobalt sulfate electrolyte and then was oxidized to form CoO on the surface. The microelectrode array (MEA) was packaged on a designed printed circuit board (PCB) for electrical connections. The MEA sensors were fully characterized with potassium sulfate solution in the concentration range of 1 x 10(-5.1)-1 x 10(-3) M at pH 7.5. The repeatable phosphate-selective potentials with a sensitivity of similar to 96 mV per decade were exhibited with less than 30 s response times and good signal stability. This sensitivity is the highest value among the reported cobalt-based phosphate sensors to date. Ultimately, in the long term, we envision extension of this MEA sensor to include additional sensors for multi-analyte, rapid, accurate and reliable in situ sensing in biological applications.