Microelectrodes interdigital

L. Yang, Y. Li, and G.F. Erf, Interdigitated array microelectrode-based electrochemical impedance immunosensor for detection of Escherichia coli 0157 H7. Anal. Chem. 76, 1107—1113 (2004). 

Figure 6. Generation/collection experiments for different fixed collector potentials in an interdigitated array of microelectrodes coated with poly(I) in CH3CN/O.I 14 [n-Bu4N]PF6. The potential of the collector electrodes is held at 0.0 V, -0.50 V, -0.59 V, -0.62 V, or -0.80 V vs. Ag+/Ag while the potential of the generator electrodes is swept between 0.0 V and -0.9 V vs. Ag+/Ag at 20 mV/s.

Figure 7. Cyclic voltammetry of an interdigitated array of microelectrodes coated with poly(I) in CH3CN/0.I H [n-Bu NlPFg (a) The potential of all eight electrodes is scanned together at 10 mV/s. (b) The potential of electrodes 2,4,6, and 8 is scanned at 10 mV/s while the potential of electrodes 1,3,5, and 7 is held at 0 V vs. Ag+/Ag.

Figure 8. Generation/colleotion experiments as a function of temperature at an interdigitated array of microelectrodes coated with poly(I) at 50 mV/s in CH3CN/O.I H [n-B NIPFg.

The determination of ammonium, arsenic, thiosulfate, allyl alcohol, and iodide has been achieved with a bromine redox mediator. Tomcik etal. [156] employ interdigitated microelectrodes at which bromine is generated at one set of electrodes and collected at a second set of electrodes. The reaction of the bromine with the analytes allows quantitative determination down to a micromolar level. 

Great activity has also been evidenced in microlithographically fabricated arrays of microelectrodes, which are typically formed in one plane on an insulating substrate [7,8,13,34-45] for experiments involving either an array of electrodes held at a common potential [37,40,42,43], or an array of noninteracting electrodes held at two or more different applied potentials [42,44], or an array of interdigitated electrodes held at two different potentials [13,34,36,38,39,45-47]. Arrays have significantly better analytical detection limits than continuous electrodes of the same overall dimensions, due to enhanced mass transport fluxes that arise from an increase in the spatial dimensionality of mass transport due to the alternation of electrode zones with pas-... 

Figure 1. Schematic representations and dimensions of interdigital microelectrodes that were coated with phthalocyanines.

L. Moreno-Hagelsieb, P.E. Lobert, R. Pampin, D. Bourgeois, J. Remade and D. Flandre, Sensitive DNA electrical detection based on interdigitated AI/AI2O3 microelectrodes, Sens. Actuators B, 98 (2004) 269-274. 

Anion detection at microelectrodes has not been studied widely. Amongst the first was the work of de Beer et al. [ 111 ] who manufactured a nitrite sensor with a tip just a few microns in diameter, which could detect nitrite ions down to 1 pM. This proved to be suitable for profiling the concentrations of nitrite anion within biofilms less than 1-mm thick inside water treatment plants. Other workers have found that use of an interdigitated microelectrode array [ 112] allows measurement of iodide via monitoring of its redox peak down to sub-micromole levels, making it a suitable technique for analysing mineral water. Carbon nanotubes coated onto Pt microdiscs have been utilised to make a nitrite sensor [113,114] with detection levels of 0.1 pM. Sulphide has also been detected at nickel microdiscs (50 pm diameter) [115]. 

Heterogeneous immunoassay has also been conducted with the antibody immobilized on beads. For instance, mouse IgG (50-100 ng/mL) was detected by ELISA in a glass chip. First, mouse IgG (antigen) was captured by magnetic beads coated with sheep anti-mouse antibody (1.02 x 107 beads/mL). Then the secondary antibody, which was rat anti-mouse conjugated with alkaline phosphatase (0.7 pg/mL), was delivered. Thereafter the substrate, PAPP, was added. It was enzymatically converted to p-aminophenol (PAP), which was electrochem-ically detected by the on-chip interdigital microelectrodes [1016]. 

DEP can be used to create regular patterns of particles on a surface or in a microfluidic channel. For example, two-dimensional (2D) patterns of polystyrene latex microbeads were fabricated on glass substrates using n-DEP, and the line- and grid-patterned microparticles, which formed due to the repulsive force of this n-DEP, were covalently bound on the substrate via cross-linking agents (Suzuki et al., 2004). In this work, interdigitated microelectrodes were incorporated into a fluidic channel in order to direct the particles into very specific patterns. 

Morita, M., Niwa, O., and Horiudii, T. (1997) Interdigitated array microelectrodes as electrochemical sensors. Electrochimica Acta, 42 (20-22), 3177-3183. 

S. Park, A. Beskok, Alternating current electrokinetic motion of colloidal particles on interdigitated microelectrodes, Analytical Chemistry, 80(8) 2832-2841 (2008). 

Field flow fraction (FFF) describes a method for separating particles based on combining a deterministic force with hydrodynamic separation. A typical configuration is shown in Fig. 11. The system consists of a channel with interdigitated microelectrodes patterned on the bottom substrate. Particles are introduced into the system and when the field is switched on they experience nDEP, moving to equilibrium positions which are defined according to the balance of dielectrophoresis (DEP) and gravity (buoyancy). Different types of particles move to different equilibrium positions in the... 

R. Pethig, Y. Huang, X. B. Wang and J. P. H. Burt, Positive and negative dielectrophoretic collection of colloidal particles using interdigitated castellated microelectrodes, J. Phys. D Appl. Phys. 24, 881-888 (1992). 

Morita M, Ni wa O and Horiuchi T 1997 Interdigitated array microelectrodes as electrochemical sensors Electrochim. Acta 42 3177-83... 

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