Millions of patients are either slowly losing their vision or are already blind due to retinal degenerative diseases such as retinitis pigmentosa (RP) and age‑related macular degeneration (AMD) or because of accidents or injuries. Employment of artificial means to treat extreme vision impairment has come closer to reality during the past few decades. Currently, many research groups work towards effective solutions to restore a rudimentary sense of vision to the blind. Aside from the efforts being put on replacing damaged parts of the retina by engineered living tissues or microfabricated photoreceptor arrays, implantable electronic microsystems, referred to as visual Prostheses, are also sought as promising solutions to restore vision. From a functional point of view, visual Prostheses receive image information from the outside world and deliver them to the natural visual system, enabling the subject to receive a meaningful perception of the image. This paper provides an overview of technical design aspects and clinical test results of visual Prostheses, highlights past and recent progress in realizing chronic high‑resolution visual implants as well as some technical challenges confronted when trying to enhance the functional quality of such devices.

until the middle of 20th century it was believed that a full understanding of the anatomy and physiology of the ear and the Neural system is required for achieving successful auditory Prostheses devices that can substitute the clever and subtle functions of the middle and inner ears and the associated Neural structures. Surprisingly however very quickly auditory implants happened to become successful enough to be an accepted clinical treatment for restoring hearing and communication abilities to individuals with profound and severe deafness and have been used by around 200, 000 people worldwide to date. Auditory implants bypass the ear and stimulate the auditory system electrically via tiny electrodes inserted in close contact with or directly inside the auditory processing structures of the brain, from where Neural activity transmits to cortical areas and produces auditory perception.

Microelectrode Arrays (MEAs) Neural interfaces are considered implantable devices that interact with the nervous system to monitor and/or modulate brain activity. Graphene-based materials are utilized to address some of the current challenges in Neural interface design due to their desirable features, such as high conductance, large surface-to-volume ratio, suitable electrochemical properties, biocompatibility, flexibility, and ease of production.In the current study, we fabricated and characterized a type of flexible, ultrasmall, and implantable neurostimulator based on graphene fibers. In this procedure, wet-spinning was employed to create graphene fibers with diameters of 10 to 50 µm. A 10-channel polyimide Printed Circuit Board (PCB) was then custom-designed and manufactured. The fibers were attached to each channel by conductive glue and also insulated by soaking them in a polyurethane solution. The tips were subsequently exposed using a blowtorch. Microstructural information on the fibers was obtained using Scanning Electron Microscopy (SEM), and the measurements of Electrochemical Impedance Spectroscopy (EIS) were conducted for each electrode.Flexible MEAs were created using graphene fibers with diameters ranging from 10 to 50 microns with a spacing of 150 microns. This method leads to producing electrode arrays with any size of fibers and a variety of channel numbers. The flexible Neural Prostheses can replace conventional electrodes in both neuroscience and biomedical research.