Electrochemical microfabricated devices

K. M. Walsh, and R. S. Keynton, Fully Integrated On-Chip Electrochemical Detection for Capillary Electrophoresis in a Microfabricated Device, Anal. Chem. 2002, 74, 3690 M. L. Chabinyc, D. T. Chiu, J. C. McDonald, A. D. Strook, J. F. Christian, A. M. Karger, and G. M. Whitesides, An Integrated Fluorescence Detection System in Poly(dimethylsiloxane) for Microfluidic Applications, Anal. Chem 2001, 73, 4491. 

Figure 6.28 Fully integrated on-chip electrochemical detection for capillary electrophoresis in a microfabricated device. (Reproduced with permission from Ref. 136.)...

Baldwin RP, Roussel Jr. TJ, Crain MM, Bathlagunda V, Jack-son DJ, Gullapalli J, Conklin JA, Pai R, Naber JN, Walsh KM, Keynton RS (2002) Fully-integrated on-chip electrochemical detection for capillary electrophoresis in a microfabricated device. Anal Chem 74 3690-3697... 

Beni V, Arrigan DWM (2008) Microelectrode arrays and microfabricaled devices in electrochemical stripping analysis. Curr Anal Chem 4 229-241... 

Miniaturization of electrochemical power sources, in particular batteries and fuel cells, has been described as a critical—but missing—component in transitioning from in-lab capability to the freedom of autonomous devices and systems. - In top-down approaches, macroscopic power sources are scaled to the microlevel usually by the use of fabrication methods, often in combination with new materials. Power generation schemes that can themselves be microfabricated are particularly appealing, as they can lead to a one-stop fabrication of device/machine function with an integrated power source. 

The present chapter reviews recent research efforts aimed at developing new devices for in situ and on-site electrochemical stripping analysis of trace metals. It is not a comprehensive review, but rather focuses on new tools for decentralized metal testing, including remotely deployed submersible stripping probes, hand-held metal analyzers coupled with disposable microfabricated strips, and newly developed green bismuth film sensors. 

R.S. Keynton, T.J. Roussel Jr., M.M. Crain, D.J. Jackson, D.B. Franco, J.F. Naber, K. Walsh and R.P. Baldwin, Design and development of microfabricated capillary electrophoresis devices with electrochemical detection, Anal. Chim. Acta, 507 (2004) 95-105. 

Lacher, N.A., Lunte, S.M., Martin, R.S., Development of a microfabricated palladium decoupler/electrochemical detector for microchip capillary electrophoresis using a hybrid glass/poly(dimethylsiloxane) device. Anal. Chem. 2004, 76, 2482-2491. 

In order to maintain the advantage of the microfabrication approach which is intended for a reproducible production of multiple devices, parallel development of membrane deposition technology is of importance. Using modified on-wafer membrane deposition techniques and commercially available compounds an improvement of the membrane thickness control as well as the membrane adhesion can be achieved. This has been presented here for three electrochemical sensors - an enzymatic glucose electrode, an amperometric free chlorine sensor and a potentiometric Ca + sensitive device based on a membrane modified ISFET. Unfortunately, the on-wafer membrane deposition technique could not yet be applied in the preparation of the glucose sensors for in vivo applications, since this particular application requires relatively thick enzymatic membranes, whilst the lift-off technique is usable only for the patterning of relatively thin membranes. 

Electrochemical devices have proven very useful for sequence-specific biosensing of DNA. Electrochemical detection of DNA hybridization usually involves monitoring a current response under controlled potential conditions. The hybridization event is commonly detected via the increased current signal of a redox indicator (that recognizes the DNA duplex) or from other hybridization-induced changes in electrochemical parameters (e.g., conductivity or capacitance). Modern electrical DNA hybridization biosensors and bioassays offer remarkable sensitivity, compatibility with modern microfabrication technologies, inherent miniaturization, low cost (disposability), minimal power requirements, and independence of sample turbidity or optical pathway. Such devices are thus extremely attractive for obtaining the sequence-specific information in a simpler, faster, and cheaper manner, compared to traditional hybridization assays. 

M. Gaitan, Fabrication and characterization of plastic microfluidic devices modified with polyelectrolyte multilayers. Proceedings—electrochemical society, 2000-19 (Microfabricated Ssrstems and MEMS V), 2000, pp. 72-79. 

There has been a trend toward electrochemical reactions in lab-on-a-chip devices in the last few years.51,52 This is mainly because miniaturized electrodes can be fabricated using microfabrication methods and solutions can be transferred by microfluidics approaches.5354 Flow injection analysis and sequential injection analysis techniques were also employed for electrochemical enantioselective high-throughput screening of drugs.55... 

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