Recessed microelectrode

M.A. McRipley and R.A. Linsenmeier, Fabrication of a mediated glucose oxidase recessed microelectrode for the amperometric determination of glucose, J. Electroanal. Chem., 414 (1996) 235-246. 

Early two-dimensional simulations focused on the evaluation of the current distribution at microdisc electrodes [107, 108] and simulations of a variety of electrode geometries [109-111] including the influence of recessed microelectrode configurations [112]. Work has been also extended to cases involving coupled homogeneous kinetics, adsorption [113], and time-dependent redox polymer electrochemistry [114]. 

Kadara, R.O., Jenkinson, N. and Banks, C.E. (2009) Screen printed recessed microelectrode arrays. Sens. Actuators, B, 142, 342. 

Fig. 15.5 Microelectrode configurations (a) disk, (b) cylinder, (c) hemisphere, (d) band, (e) ring, (f) sphere cap, (g) cone, (b) nanopore, and (i) recessed microelectrode...

Sheep heart Purkinje fibers closed end, recessed up—all-glass microelectrode Na- 7.3mM 147)... 

For the sake of completeness, glass microelectrodes [48, 59, 184] will first be mentioned. Two types of these electrodes are used, spear-shaped microelectrodes [59] and recessed-tip microelectrodes [165] (see fig. 4.5). In the former case, the microelectrode is drawn from a capillary of an ion-exchanger glass and is insulated on the outside, except for the tip, by inserting the microelectrode into a micropipette made of an inactive glass. In the latter case, the outer micropipette extends over the microelectrode tip. The two capillaries are sealed together and the ISM is in contact with the liquid between the two capillaries. 

Fig. 4.5. Two types of ion-sensitive glass microelectrodes (a) Hinke s spear type (b) recessed-tip type. (After J. L. Walker [1841.)...

The UMDE evinces strong edge effects or very uneven current densities along the radius of the disk. It shares this problem with all the other flat microelectrodes such as microbands or rings. The exception of course are the hemispherical or hemicylindrical microelectrodes, which have no effective edges and behave as half of a sphere or cylinder, and also deeply recessed disks or bands, which approach the shrouded types. 

General Aspects It is beyond the scope of this treatment to discuss the current and potential distribution for photoresist microelectrodes in detail. Therefore, only a few comments will be made on the influence of the geometry and the resist barrier on electrochemical measurements. Photoresist microelectrodes can be treated as a recessed microdisk electrode. The diffusion field and the current distribution are... 

Sheep heart Purkmje fibers Na closed end, recessed tip—all-glass microelectrode Na 7.3 mM E4... 

FIG. 1 Schematic cross sections of selected microelectrode configurations, (a) Nomenclature for parts of microelectrode, (b) Na+-sensitive microelectrode (22), (c) recessed-tip Na+-sensitive microelectrode (27), (d) liquid ion-exchanger micropipette electrode (38), (e) coated wire electrode (16), (f) flow-through ISE (e.g., NOVA 6, Boehringer ISE 2020), (g) micro-capillary glass electrode of tubular shape (e.g., Radelkis OP-266), (h) planar sensor fabricated by microelectronic technology (93), (i) ISFET sensor (94). 

Saunders and Brown (38) reported a method to prepare recessed tip silver/silver chloride microelectrodes. In the first step of this procedure they electrochemically sharpened the end of a silver wire (diameter 125 /xin) by dipping it into basic sodium cyanide solution and anodizing it under voltage control. This was followed by an electrochemical chloride-coating step in 100 mM HC1 solution. 

In recent years, recessed-top microelectrodes have come into use for inserting into living cells and recording changes in pH during several hours (Thomas,... 

G. Grancharov, E. Khosravi, D. Wood, A. Turton, and R. Kataky. Individually addressable recessed gold microelectrode arrays with monolayers of thio-cyclodextrin nanocavities. Analyst. 130, 1351-1357 (2005). 

F. A. Aguiar, A. J. Gallant, M. C. Rosamond, A. Rhodes, D. Wood, and R. Kataky, Conical recessed gold microelectrode arrays produced during photolithographic methods Characterisation and causes, Electrochem. 

A comparison of the chronoamperometric response at inlaid and recessed disc microelectrodes. J Electroanal Chem 249 1-14... 

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