An implantable microactuated intrafascicular electrode for peripheral nerves.

Important advancements have been recently achieved in the field of neural interfaces to restore lost sensory and motor functions. The aim of this letter was to develop an innovative approach to increase the selectivity and the lifetime of polyimide-based intrafascicular electrodes. The main idea was to obtain a neural interface that is able to restore a good signal quality by improving the electrical connection between the active sites and the surrounding axons. The high flexibility of polyimide-based neural interfaces allows to embed microactuators in the interface core and achieve desired microdisplacements of the active sites. Nearly equiatomic nickel-titanium alloy was selected as a microactuator because of its shape memory effect. A single TiNi thin film was obtained by dc magnetron sputtering, and was segmented into four distinct sectors. This solution allowed the independent actuation of the different active sites (multiactuation). A corrugated profile was impressed to the new actuated intraneural (ACTIN) interface. The active sites were positioned in correspondence to the peaks of the corrugation, thus maximizing the effects of the single actuations. The technological results, the electrical properties, the thermal behavior, and eventually, the actuation performances of the current ACTIN prototype are shown and discussed. The actuation cycle was thermally compatible for biomedical applications. Promising results were obtained from the current ACTIN prototype with an average controlled movement of 7 microm of the peaks.

An optically powered single-channel stimulation implant as test system for chronic biocompatibility and biostability of miniaturized retinal vision prostheses.

A microsystem based microimplant with an optically powered single-channel stimulator was designed and developed as test system for an epi-retinal vision implant. Biostability of the hybrid assembly and the encapsulation materials were evaluated in pilot experiments in chronic implantations in a cat animal model. The implant was fabricated on a flexible polyimide substrate with integrated platinum electrode, interconnection lines, and contact pads for hybrid integration of electronic components. The receiver part was realized with four photodiodes connected in series. A parylene C coating was deposited on the electronic components as insulation layer. Silicone rubber was used to encapsulate the electronics in the shape of an artificial intraocular lens to allow proper implantation in the eye. Pilot experiments showed the biostability of the encapsulation approach and full electric functionality of the microimplant to generate stimulation currents over the implantation period of three months in two cats. In one cat, electrical stimulation of the retina evoked neuronal responses in the visual cortex and indicated the feasibility of the system approach for chronic use.