| Popis: |
The realization of a standard chemical or ion-selective electrode in a thick film (T-F) or ‘hybrid’ form is not merely an engineering exercise. Many problems, both chemical and physical in nature, have to be solved. A general guide for the development of hybrid devices is contained in four basic questions: (i) How do T-F methods of deposition affect the sensing materials, i.e. will there be any change in morphology or chemical composition, and if so, how can this be remedied? (ii) Can the sensing material, normally an ionic conductor, be interfaced successfully with an electronic conductor? Most ion-selective materials (ISMs) are conventionally used as membranes and electrical connection is via a solution phase. A solid back contact poses questions of reversibility and hence stability. (iii) Will the active surface of the sensor withstand the relatively high temperatures used in the T-F deposition process? (iv) Has the ISM the physical requirements necessary for planar structures, e.g. a thermal expansion coefficient compatible with that of the substrate over the required temperature range? Is the chemical polarity of the material compatible with that of standard encapsulants? |
