Electrodes flexible wire

See Figure 7.33 and Section 7.13. The electrode wire is a trivial but very important part of the electrode. There are many things to consider the best cable track, no wire drag on the electrode, and minimal weight of the electrode connector. Very flexible wire, perhaps shielded The best is to have no connector at the electrode side, a wire with prefabricated direct entry into the electrode. 

Cables, wires, and connectors. Remedies light and flexible wires, carefully prepared wire tracks, and wire fixation with small wire loops allowing patient to move without wire pulling the electrode. Each electrode wire before leaving the body could be terminated in a small box, with common cable further from the body up to the electronic instrument. Tiny box with preamplifiers near the patient. Prewired electrodes are without the weight of local connector and plug. 

A further design problem is that the eleetrodes themselves must be flexible enough to expand and contract without significantly restraining the volume changes of the gel. This can be achieved with flexible wire electrodes or some other type of soft electrode system. 

The connections are thus normally made to the edge of the electrode. Simple wires connect the positive of one cell to the negative of another. This gives a certain flexibility it is not necessary to connect the positive of one cell to the negative of the adjacent ceU, as must occur with bipolar plates. Instead, complex series/parallel connections can be made, as in Figure 5.9. 

Many other opportunities exist due to the enormous flexibility of the preparative method, and the ability to incorporate many different species. Very recently, a great deal of work has been published concerning methods of producing these materials with specific physical forms, such as spheres, discs and fibres. Such possibilities will pave the way to new application areas such as molecular wires, where the silica fibre acts as an insulator, and the inside of the pore is filled with a metal or indeed a conducting polymer, such that nanoscale wires and electronic devices can be fabricated. Initial work on the production of highly porous electrodes has already been successfully carried out, and the extension to uni-directional bundles of wires will no doubt soon follow. 

An alternative method to position two electrodes at nanometer distances apart is the mechanically-controlled, break junction (MCBJ) technique. An ultra-thin, notched Au wire on a flexible substrate can be broken reliably by pushing on the Au with a piezoelectric piston, cracking the Au (Fig. 4). This produces a gap between the Au shards whose size can be finely varied to 1 A by a piston or control rod [46, 47]. When UE molecules with thiol groups on both ends are present in a surrounding solution, the gap can be adjusted until the molecules can span it. A dilute solution means the number of spanning molecules will be small, and the least-common-multiple of current flow among many junctions indicates those spanned by a single molecule [47]. 

Figure 1. Diagram of Teflon cell (1) platinum electrode (2) glass scintillator (3) Macor ceramic disk cell bottom (H) Teflon O-ring (5) flexible elbow (see insert) (6) cell ports (six of them around cell body) (7) light pipe. Inset shows the details of the flexible elbow (8) stainless steel sphere (9) concave Teflon spacer (10) platinum wire for electrical connection across elbow (11) lock nut.

Figure 13. A redox enzyme electrically wired to an electrode surface by flexible polymer chains functionalized with redox-mediator groups and surrounding the enzyme at the electrode surface.

Enzyme biosensors containing pol3mieric electron transfer systems have been studied for more than a decade. One of the earlier systems was first reported by Degani and Heller [1,2] using electron transfer relays to improve electrochemical assay of substrates. Soon after Okamoto, Skotheim, Hale and co-workers reported various flexible polymeric electron transfer systems appUed to amperometric enz5une biosensors [3-16], Heller and co-workers further developed a concept of wired amperometric enzyme electrodes [17—27] to increase sensor accuracy and stability. 

Electric resistivity. The electric resistance measurement is the same as discussed below under volume resistivity, to which this measurement is temporary adapted. For flexible materials, special electrode systems are developed to clamp sample and electric wires. The measuring equipment is based on a Wheatstone bridge circuit. The conductivity of metal powder-containing epoxy was measured in special dies equipped with built-in brass electrodes inserted to the die. The material was cured in the die to assure good contact with electrodes. Special sample holders and clamping devices are used for precise determination of rubber compounds containing carbon black. ... 

Tool-electrodes can be fabricated in several ways. An excellent and flexible solution is wire electrical discharge grinding (WEDG), which is well suited for microfabrications [85]. An alternative way is to use anodic etching of tungsten. As shown by Lim et al. [82] very thin cylindrical electrodes (down to 50 pm) with controlled diameters can be fabricated. The important point is to use a high concentration of the electrolyte (typically 5 M KOH) and relatively high current densities around 10 mA/mm2. Thus, the diffusion layer around the electrode can be controlled in order to achieve various tool shapes by anodic... 

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