MEMS Needle-type Sensor Array for in Situ Measurements of Dissolved Oxygen and Redox Potential

Abstract

Microelectrodes are among the most accurate and reliable monitoring devices for measuring the dynamics of biofilm processes. This paper describes a novel needle-type microelectrode array (MEA) for simultaneous in situ measurements of dissolved oxygen (DO) and oxidation reduction potential (ORP) fabricated using microelectromechanical systems (MEMS) technologies. The MEA exhibits fast response times for both DO and ORP measurements and shows a substantial increase in DO sensitivity. To demonstrate the versatility of the new sensor, it was applied to the measurement of DO and ORP microprofiles in a multispecies biofilm. This work demonstrates that the MEA is able to monitor local concentration changes with a high spatial resolution and provide the versatility of the microelectrode technique needed for biofilm studies as well as the capability for repetitive measurements. In addition, the use of MEMS technologies and batch fabrication approaches enables integration, high consistency, high yields, and mass production. With further development, it may be possible to add additional sensors to the MEA (e.g., pH, phosphate) and integrate them with a reference electrode.

CO 2 Production as an Indicator of Biofilm Metabolism

“…Techniques that provide information about the physical structure and chemical properties of biofilms are nuclear magnetic resonance (44), attenuated total reflectance-Fourier transform infrared spectroscopy (7), and photoacoustic spectroscopy (43). Some biofilm monitoring techniques provide information about metabolic activity in biofilms, such as those using electrochemical devices like dissolved oxygen and redox probes (25), microbiologically influenced corrosion monitoring (34), nuclear magnetic resonance (56), measurement of substrate consumption (19,50) or metabolic products (53), bioluminescence assays, and fluorometry (56).…”

Fabrication of a needle-type pH sensor by selective electrodeposition

“…Since current application is necessary for electrodeposition, application of current to specific pads of a packaged sensor results in selective deposition of the IrOx film. Thus, this approach offers the ability to selectively deposit metallic films at the tips of specific needle sensors, paving the way to integration of the pH sensor with the previously described needle-type ORP 4,5 and DO 6,7 sensors. Taking this approach further, different metallic films may be deposited at the tips of different needle sensors, permitting future integration of the pH sensor with the recently described phosphate sensor based on the cobalt oxide sensing layer.…”

“…1,3 Microelectromechanical system (MEMS) technologies can offer many advantages to fabrication and integration of sensors, including reduced sensor complexity, increased reproducibility (and yield) of the fabrication process, and reduced costs due to batch fabrication. We recently applied MEMS technologies to the development of microelectrode arrays (MEAs) for measurement of the oxidation-reduction potential (ORP) 4,5 and dissolved oxygen (DO). 6,7 ORP is a measure of the solution potential and thus ORP MEA sensors are non-specific and measure the oxidized and reduced forms of all chemical species in the solution.…”

An array of individually addressable micro-needles for mapping pH distributions

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Silicon has been used predominantly for fabrication of microneedles, however the fragility and the cost of the microfabrication process are major drawbacks for this material. [1][2][3][4] Injection molding has instead emerged as an alternative fabrication process offering advantages such as cost and robustness.…”