Hydrogels electrode

Figure 7.3 Exploded view of the Cygnus GlucoWatch showing the components of the disposable hydrogel electrode and the underlying reusable electronic leads. Reprinted with permission from Ref. 6. Copyright 2001 Elsevier.

FIGURE 4.4 Examples of different skin electrodes (a) metal plate electrodes, (b) suction electrode for EGG, (c) metal cup EEG electrode, (d) recessed electrode, (e) disposable electrode with electrolyte-impregnated sponge (shown in cross section), (f) disposable hydrogel electrode (shown in cross section), (g) thin-film electrode for use with neonates (shown in cross section), and (h) carbon-filled elastomer dry electrode. 

Figure 7.19 shows the same data for hydrogel and aluminum electrode metal. Series resistance flattens out at about 1500 O at higher frequencies left part of the diagram of Figure 7.19. This corresponds to a conductivity of the hydrogel equal to a = 6 mS/m (gel thickness 1 mm). Accordingly, the polarization impedance down to about 0.1 Hz of this hydrogel electrode is purely resistive and dominated by the frequency independent resistance of the gel.

Figure 17.6 Redox hydrogel approach to immobilizing multiple layers of a redox enzyme on an electrode, (a) Structure of the polymer, (b) Voltammograms for electrocatalytic O2 reduction by a carbon fiber electrode modified with laccase in the redox hydrogel shown in (a) (long tether) or a version with no spacer atoms in the tether between the backbone and the Os center (short tether). Reprinted with permission fi om Soukharev et al., 2004. Copyright (2004) American Chemical Society.

A.L. Crumbliss, J.Z. Stonehuerner, R.W. Henkens, J. Zhao, and J.P. O Daly, A carrageenan hydrogel stabilized colloidal gold multi-enzyme biosensor electrode utilizing immobilized horseradish peroxidase and cholesterol oxidase/cholesterol esterase to detect cholesterol in serum and whole blood. Biosens. Bioelectron. 8, 331-337 (1993). 

Porous catalytic pellets, 25 271-272 Porous electrodes, 3 428-429 Porous glass, 22 394 Porous graphite, 12 747 Porous hydrogels, for tissue engineering, 13 750-751... 

Electrode surfaces can be modified by redox polyelectrolytes via a sol-gel process, yielding random redox hydrogels or by layer-by-layer self-assembly of different redox and nonredox polyelectrolytes by alternate electrostatic adsorption from solutions containing the polyelectrolytes to produce highly organized redox-active ultrathin multilayers. 

Using a glassy carbon electrode modified with a mercury film, Weber et al. [66] measured the association and dissociation rate constants for the complex formed between Pb + and the 18-crown-6 ether. It was found that Pb + forms a complex with 18-crown-6 with a stoichiometiy of 1 1 in both nitrate and perchlorate media. The formation constant, for the nitrate and perchlorate systems are (3.82 0.89) X 10 and (5.92 1.97) x lO mol Ls , respectively. The dissociation rate constants, are (2.83 0.66) x 10 with nitrate and (2.64 0.88) x 10 s with perchlorate as counter ion. In addition, the binding of Pb + with benzo-18-crown-6 embedded in a polymerized ciystalline colloidal array hydrogel has been also analyzed [67]. 

Ivekovic et al. [42] Fruit juice, yoghurt drink Glucose oxidase (GOx)/ into palladium hexacyanoferrate (PdHCF) hydrogel Nickel hexacyanoferrate (NiHCF) electrodeposited onto graphite electrode/-0.075V vs. SCE Nickel hexacyanoferrate... 

Patel et al. [9] Wine Alcohol oxidase (AOx)/with poly(carbamoyl)sulfonate (PCS) hydrogel containing PEI Screen-printed platinum electrode/ +600 mV vs. Ag/AgCl -... 

---