The paper reports on the deposition of iridium oxide thin films by dc reactive magnetron sputtering and their characterization by surface analysis methods (X-ray diffraction, scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy) and electrochemical techniques (cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic square waves). The sputtering process was investigated by applying the method of generic curves. An optimal combination of sputtering parameters has been established [40 standard cubic centimeters per minute (sccm) argon/8-12 sccm oxygen/40% effective pump power/100 W dc power/“cold” sputtering] that yields stable microporous amorphous films with a highly extended surface. These films have shown an excellent electrochemical reversibility in physiological saline solution with a “safe” potential range of −1.2 to 1.3 V vs. Ag/AgCl reference electrode, a charge delivery capacity of 90-95 mC/cm2, a constant impedance of 70-80 Ω in the frequency range of 100 kHz down to 0.5-1.0 Hz, and a quick response to bipolar current pulses with a safe charge per phase of 2 mC/cm2/ph. The demonstrated remarkable electrochemical characteristics combined with their established long-term mechanical stability and corrosion resistance allow one to recommend the use of sputtered iridium oxide films as an ideal electrode material for neural stimulation. © 2004 The Electrochemical Society. All rights reserved.

The EPIRET3 system can be successfully implanted and explanted in patients with blindness and RP. The surgical steps are feasible, and the postoperative follow-up disclosed an acceptable range of adverse events.

In industrial-scale biotechnological processes, the active control of the pH-value combined with the controlled feeding of substrate solutions (fed-batch) is the standard strategy to cultivate both prokaryotic and eukaryotic cells. On the contrary, for small-scale cultivations, much simpler batch experiments with no process control are performed. This lack of process control often hinders researchers to scale-up and scale-down fermentation experiments, because the microbial metabolism and thereby the growth and production kinetics drastically changes depending on the cultivation strategy applied. While small-scale batches are typically performed highly parallel and in high throughput, large-scale cultivations demand sophisticated equipment for process control which is in most cases costly and difficult to handle. Currently, there is no technical system on the market that realizes simple process control in high throughput. The novel concept of a microfermentation system described in this work combines a fiber-optic online-monitoring device for microtiter plates (MTPs)--the BioLector technology--together with microfluidic control of cultivation processes in volumes below 1 mL. In the microfluidic chip, a micropump is integrated to realize distinct substrate flow rates during fed-batch cultivation in microscale. Hence, a cultivation system with several distinct advantages could be established: (1) high information output on a microscale; (2) many experiments can be performed in parallel and be automated using MTPs; (3) this system is user-friendly and can easily be transferred to a disposable single-use system. This article elucidates this new concept and illustrates applications in fermentations of Escherichia coli under pH-controlled and fed-batch conditions in shaken MTPs.

This paper describes the reactive RF-powered sputter deposition of iridium oxide (IrOx) to be used as the active stimulation layer in functional medical implants. Using an approach based on generic curves, the amount of oxygen gettered by the film is determined for various carrier gas flows and pumping speeds. It is shown that under certain conditions the getter effect peaks in the shape of a plateau when increasing the oxygen supply to the chamber. Films deposited along this curve show strong differences in electrochemical behaviour. At the beginning of the plateau, stable films with high electrochemical activity are deposited, and impedance measurements link the increase in charge delivery to a higher active surface area. On depositing at the far side of the plateau, the maximum deposition rate is recorded; however, unstable films are formed. These films predominantly contain unstable iridium oxide species, with iridium atoms in higher valence states. Protein adsorption, as is known to occur at implanted electrodes, was tested on some samples, and does not deteriorate the IrOx characteristics.

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