Spatially Controlled Membrane Depositions for Silicon-Based Sensors

The membrane deposition technology on silicon-based transducers constitutes the most delicate part of the miniaturized (bio)chemical sensor fabrication. Membrane adhesion to the transducer, reproducibility of the deposition process and its spatial control are the three most important parameters which determine the sensor performance and lifetime.The fabrication of two sensors is described: 1) a combined pO2, pCO2, pH sensor for which a polyacrylamide gel and a polysiloxane gas-permeable membrane were deposited and patterned at the on-wafer level and 2) a glucose amperometric enzyme electrode where the glucose oxidase was immobilized electrochemically either in a polypyrrole matrix or co-deposited with bovine serum albumin by electrochemically aided adsorption. The optimization of the deposition procedures allowed reproducible devices with reasonable lifetimes to be obtained

Modification des polymères conducteurs avec de petites particules métalliques; propriétés des films de polypyrrole et de polyaniline platines

The properties of two π-conjugated conducting polymers, polypyrrole, and polyaniline, modified with small amounts of Pt, have been investigated. Both polymers were prepared by electrochemical (cyclic voltammetric) polymerization in the form of thin films (less than 1 μm for polypyrrole, ca. 50-μm thick for polyaniline). It is shown that incorporation, via electrodeposition, of small amount of dispersed Pt particles, inside the polymer film, leads to radical change of its properties. Thus, the polypyrrole film electrode containing ca. 200 μg · cm-2 of Pt exhibits remarkably stable electrocatalytic activity towards anodic oxidation of an important fuel cell reactant – CH3OH. In contrast with the bulk Pt metal or the Pt dispersed on other supports, a polypyrrole/Pt composite does apparently not undergo poisoning, even in the course of prolonged oxidation runs. We show also that the incorporation of Pt microparticles, into several tens of μm thick polyniline films, results in a large enhancement of their redox switching rate between isolating and conducting states and vice versa

Microfabricated Chemical Analysis Systems for Environmental Applications

Recent contributions to the design, development, and fabrication of microtechnological devices for chemical analysis are summarized. The discussion includes microdisk-electrode arrays for voltammetric analysis of trace metals, and micro total-analysis systems for coulometric nanotitrations of different analytes

Theoretical treatment and computer simulation of microelectrode arrays

New relations for and interrelations between the current responses of different microelectrode arrays are presented. Interdigitated microelectrode arrays (IDAs: alternating cathodes and anodes) and uniform microband electrode arrays (MEAs: only cathodes or anodes) are treated, and miniaturized systems with planar band electrodes or hemicylinder electrodes are discussed. A common basis was found for the specific response characteristics of IDAs and MEAs. The theoretical expressions were verified by results from computer modelling. The numerical simulations made use of finite-element procedures to evaluate steady-state and time-dependent mass fluxes and concentration profiles of electroactive species at the surfaces of different microelectrode arrays. It was shown that the response behavior of a given array can be exactly predicted from the current data of other arrays