Bulk biocatalyst elements

In those cases where the transducer element does not lend itself to bulk manufacture and disposal after use, an alternative approach is to arrange for the biological component to be incorporated in a low-cost disposable unit, with a simple method for replacement when necessary. This is particularly suitable for flow-through-type measurement systems, where the biocatalyst can be upstream of the transducer - as in the flow-injection analysis (FIA) approach to monitoring. 

The conceptual theme of hierarchically stractured materials that are specifically designed to maximize anode or cathode performance can be separately considered in the following components (1) the bulk electrode materials, (2) pores in the bulk material that accommodate fluid flow, (3) mesoporous or structural material to transition from the bulk material to the nanometric dimensions, (4) the nanostmctured transducer, (5) the bio-nano interface, and (6) the biocatalyst (Figure 10.1) [23]. All of the elements must be coupled to achieve electron flow from the electron donor through the architecture to the final electron acceptor. In the anodic half-cell, fuel is oxidized and the liberated electrons are transferred to the electrode and through an external load. The cathode provides the BFC with electromotive force by catalyzing the reduction of oxygen at relatively positive potentials. 

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