Needle-type environmental microsensors: design, construction and uses of microelectrodes and multi-analyte MEMS sensor arrays

Abstract

The development of environmental microsensor techniques is a revolutionary advance in the measurement of both absolute levels and changes in chemical species in the field of environmental engineered and natural systems. The tiny tip (5-15 μm diameter) of microsensors makes them very attractive experimental tools for direct measurements of the chemical species of interest inside biological samples (e.g., biofilm, flocs). Microelectrodes fabricated from pulled micropipettes (e.g., dissolved oxygen, oxidation-reduction potential, ion-selective microelectrode) have contributed to greater understanding of biological mechanisms for decades using microscopic monitoring, and currently microelectromechanical system (MEMS) microfabrication technologies are being successfully applied to fabricate multi-analyte sensor systems for in situ monitoring. This review focuses on needle-type environmental microsensor technology, including microelectrodes and multi-analyte MEMS sensor arrays. Design, construction and applications to biofilm research of these sensors are described. Practical methods for biofilm microprofile measurements are presented and several in situ applications for a biofilm study are highlighted. Ultimately, the developed needle-type microsensors combined with molecular biotechnology (such as microscopic observation with fluorescent probes) show the tremendous promise of micro-environmental sensor technology.

Stretchable, Multiplexed pH Sensors With Demonstrations on Rabbit and Human Hearts Undergoing Ischemia

“…All sensitivity values were consistent with previous reports of electrochemically deposited IrO x electrodes. [1,2,17,19–22,26–29]…”

“…[26,27] In fact, most pH sensors made with electrodeposited IrOx exhibit sensitivities between 65 and 75 mV/pH at room temperature. [1,2,17,19–22,26–29]…”

“…[18] Such electroplated iridium oxides are known to provide levels of precision and reproducibility in pH sensing electrodes that are superior to those of counterparts form by physical vapor deposition or high-temperature growth. [19–22]…”

Recent Advances in Information and Communications Technology (ICT) and Sensor Technology for Monitoring Water Quality

“…Commercially available CDT instruments use conductometric electrodes to measure salinity, Ag 2 S electrodes to measure sulfur, and potentiometric methods to detect oxygen and nitrous oxide. The phosphate ion electrode is one of the most important parts of the sensing system, and it has been proposed to use a cobalt (Co)-based phosphate microelectrode because Co is a phosphate-sensitive electrode material [28,29]. Micro-electro mechanical systems (MEMS) conjugated with microelectrode array sensors have been developed for the detection phosphate and showed robust and precise in situ measurements and multi-analyte detection with a small amount of sample volumes; but due to the configuration of the microelectrode array sensors, it may be fragile under high-flow or turbulent water environments [30].…”

Characterization of Resonant Mass Sensors Using Inkjet Deposition

“…Microscale devices lend themselves towards sensing applications due to the high sensitivity of their mechanical behavior to changes in system parameters (such as mass, stiffness, or damping), boundary conditions and various external fields. The promise associated with this high sensitivity has motivated the development of resonant sensors suitable for general mass sensing [1][2][3][4][5][6], as well as chemical and biological sensing [7][8][9][10][11][12][13][14][15][16][17][18]. As a specific example, prior art exists wherein resonant microscale sensors are used to detect explosive materials [19][20][21][22].…”