Three forces induced by magnetic fields offer unique control of fluid motion and new opportunities in microfluidics. This article describes magnetoconvective phenomena terms the theory controversy, tuning redox processes at electrodes, early-stage applications analytical chemistry, mature disciplines far afield, future directions for micro total analysis systems. (To listen to a podcast about this article, please go Analytical Chemistry multimedia page pubs.acs.org/page/ancham/audio/index.html .).

A self-contained, microelectrochemical immunoassay on the smallest volumes reported to date (1 μL for antigen, 1 secondary antibody−enzyme conjugate, and 200 nL electrochemically detected species) has been developed using mouse IgG as a model system in sandwich-type enzyme-linked immunosorbant assay, which takes less than 30 min both complete assembly of components onto antibody-modified surface detect enzymatically generated species (excluding time electrochemical cleaning electrodes)....

This paper describes a robust and reliable process for fabricating novel sputter-deposited, thin-film carbon microelectrode array using standard integrated circuit technologies silicon micromachining. Sputter-deposited films were investigated as potential candidates materials. The surface properties cross section of the arrays studied by atomic force microscopy scanning electron microscopy, respectively. Electrical site impedance, crosstalk, lifetime (dielectric integrity) microelectrodes in...

Dopamine, the main catecholamine neurotransmitter in brain, is predominately produced basal ganglia and released to various brain regions including frontal cortex, midbrain brainstem. Dopamine's effects are widespread include modulation of a number voluntary innate behaviors. Vigilant regulation dopamine levels throughout imperative for proper execution motor behaviors, particular speech other types vocalizations. While dopamine's role circuitry widely accepted, its unique function normal...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPotential-Dependent Stability of Self-Assembled Organothiols on Gold Electrodes in Methylene ChlorideW. Russell. Everett, Timsey L. Welch, Laura. Reed, and Ingrid. Fritsch-FaulesCite this: Anal. Chem. 1995, 67, 2, 292–298Publication Date (Print):January 15, 1995Publication History Published online1 May 2002Published inissue 15 January 1995https://pubs.acs.org/doi/10.1021/ac00098a010https://doi.org/10.1021/ac00098a010research-articleACS...

Redox magnetohydrodynamics (RMHD) microfluidics is coupled with dark-field microscopy (DFM) to offer high-throughput single-nanoparticle (NP) differentiation in situ and operando a flowing mixture by localized surface plasmon resonance (LSPR) tracking of NPs. The color the scattered light allows visualization NPs below diffraction limit. Their Brownian motion 1-D superimposed on perpendicular RMHD trajectory yields their diffusion coefficients. LSPR coefficients provide two orthogonal...

An electrochemical enzyme-linked immobilized DNA-hybridization assay for the detection of Cryptosporidium parvum in water has been developed. The target molecule was a 121-nucleotide sequence from C. heat shock protein 70 (hsp70 mRNA U71181 gene). This analyte offers possibility distinguishing dead live oocysts. involves covalent attachment primary DNA probe via its 5'-amine-terminus to self-assembled monolayers mercaptoundecanoic acid gold surface. used capture (sequence 1039−1082...

Amperometric detection at microelectrodes in lab-on-a-chip (LOAC) devices lose advantages signal-to-background ratio, reduced ohmic iR drop, and steady-state signal when volumes are so small that diffusion fields reach the walls before flux becomes fully radial. Redox cycling of electroactive species between multiple, closely spaced offsets limitation provides amplification capabilities. A device integrates a microchannel with an individually addressable microband electrode array has been...

Abstract A simple, fast, reproducible (2.5% RSD at 3.0 μg/L), and sensitive method is described for quantifying As(III) (0.3 μg/L detection limit, 0.5–440 dynamic range). Anodic stripping voltammetry (ASV) performed after accumulating arsenic a mercury film electrode −0.350 V vs. Ag/AgCl (saturated KCl) 20 s in 0.2 M HCl containing 8 μM ammonium 2‐amino‐1‐cyclopentene‐1‐dithiocarboxylate (AACD), without oxygen removal. This the first report of using AACD ASV electrochemical quantification...

Exchange of self-assembled monolayers (SAMs) dodecanethiol (C12H25SH) on gold with decanethiol (C10H21SH) was detected laser-desorption Fourier transform mass spectrometry (LD-FTMS) in the negative ion mode. The amount adsorption C10H21SH is dependent extent air oxidation C12H25SH SAM. In this study, a partially oxidized SAM 2.2:1.5:1 ratio dodecanethiolate (C12H25S-, m/z 201) to presumed dodecanesulfinate (C12H25SO2-, 233) dodecanesulfonate (C12H25SO3-, 249) surface examined. After sample...

A new generation of platinum nanoelectrodes for constant-distance mode scanning electrochemical microscopy (CD-SECM) has been prepared, characterized, and used high spatial resolution measurements visualization electrochemically induced concentration gradients in microcavities. The probes have long (1−2 cm), narrow quartz tips that were conically polished a Pt nanoelectrode is slightly offset from center. Because the size location electrode on probe, it does not exhibit SECM feedback while...

Natural convection actuated by electrochemically-generated density gradients at microelectrodes was investigated under different conditions simultaneously visualizing fluid flow with the electrochemical response. The studies elucidate deviations of behavior from theoretical expectations and parameters that control natural convection, which can be exploited in electroanalysis, microfluidics, electrodeposition. Experiments involved an enclosed, small volume containing 0.00475-0.095 M each...

Construction and characterization of microfabricated recessed microdisk electrodes (RMDs) 14- 55-μm diameters 4-μm depth are reported. For evaluation electrode function, both faradaic current in Ru(NH3)63+/KNO3 solution charging KNO3 were measured with cyclic voltammetry. The experimental maximum was compared to calculated values, assuming radial linear diffusion. A model for diffusion a RMD best matches the behavior 14-μm RMD, which has larger depth-to-diameter ratio than RMD. At fast scan...

Useful analytical application of submicrometer band electrodes depends strongly upon developing reproducible, convenient fabrication and characterization procedures. We report arrays individually addressable that are 2 mm long functional down to 37.0 nm in width, using multilayered materials conventional microfabrication techniques. Fabrication involves thermal vapor deposition a chromium adhesion layer gold on glass, followed by plasma-enhanced chemical silicon nitride layer,...

By adding redox species, both aqueous and nonaqueous solutions can be pumped along the length of a microfluidic channel when low voltages (to produce current) are applied across channel's breadth in presence magnetic field its height. Control flow rate is possible by varying magnitudes voltage changing concentration. Direction determined polarity orientation. We have demonstrated dc magnetohydrodynamic (MHD) pump microchannels ( wide deep long) that were constructed from low-temperature...

Microbeads are used to track fluid flow over microband electrode arrays investigate fundamentals of redox magnetohydrodynamics (redox-MHD) in a confined solution. The results may lead toward the design micro total analysis systems with microfluidics based on redox-MHD concept. Ion flux was generated by reduction and oxidation electroactive potassium ferri- ferrocyanide at selected individually addressable microelectrodes array. An external magnetic field produced small, permanent magnet...