Wireless retina implant with large visual field

We present the concept of a novel epiretinal prosthesis, consisting of a foil-based, miniaturized electronics with wireless optical energy and signal transmission and integrated electrostimulation. The aim is achieving a wideangle projection to create a large visual field. The implant having a diameter of 14 mm consists of a mosaic-like array of thinned silicon-based photodiodes combined with a polyimide foil. This thin implant, realized on a flexible foil for the first time, adapts to the curvature of the eye. Thin-film stimulation electrodes on the foil are electrically connected to the photodiodes. The influence of the electrode geometry on the electrical current density at the location of electrostimulation is investigated by computer simulations. First experiments towards realization of via holes in a 10 μm thick polyimide layer were successful and led to vias with inclined sidewalls and rounded openings. This shape is advantageous concerning uninterrupted conductor paths leading from the photodiodes to the stimulation electrodes.

Niobium-Containing DLC Coatings on Various Substrates for Strain Gauges

Niobium-containing diamond-like carbon films (a-C:H:Nb) were deposited in a hybrid plasma-enhanced chemical vapor deposition (PECVD) and direct-current magnetron sputtering (DCMS) process, using a niobium target in an argon/acetylene atmosphere on industrial polyimide foil, spin-coated polyimide foil, and alumina substrates. While the coating on the industrial foil tends to crack, the thin films on the spin-coated polyimide and the ceramic substrates showed good adhesion, as well as a smooth and dense topography. Investigations of the electrical properties revealed their suitability as biocompatible sensor materials in strain gauges, with a gauge factor of up to 3.2 and a temperature coefficient of the electrical resistance (TCR) of −200 ppm/K.