Scientists from Chalmers University of Technology in Sweden, the University of Freiburg, and the Netherlands Institute for Neuroscience have developed an ultra-small implant, featuring electrodes the size of a single neuron, which holds potential for future vision restoration treatments for the blind. This unique innovation combines miniaturized size with long-lasting durability once inserted into the body.
Blindness often occurs due to damage in parts of the eye, while the visual cortex in the brain remains functional and ready for stimuli. Vision restoration through brain stimulation requires thousands of electrodes within an implant to construct an image through the transmission of electrical impulses to the brain’s visual cortex. Each electrode contributes to creating one pixel of the image.
The image developed using such electrical impulses, according to Maria Asplund, Professor of Bioelectronics at Chalmers University of Technology and the project’s technology development leader, is akin to a highway’s matrix board, featuring a dark space with illuminated spots based on received information. The more electrodes contributing, the sharper the image.
The vision implant developed in this research resembles a ‘thread’ with numerous electrodes arranged linearly. The eventual goal is to have multiple threads, each connected to thousands of electrodes, enabling a more comprehensive implant.
Vision restoration through electrical implants isn’t a novel idea. However, current implant technology, dating back to the 90s, has several limitations, such as a large size causing brain scarring, corrosion over time, and inflexible materials. The researchers’ creation of a neuron-sized electrode allows for a more detailed image and a durable vision implant due to the flexible, non-corrosive materials used.
However, the smaller the implant size, the greater the risk of corrosion, especially within the harsh conditions of the human body. The main challenge lies not in miniaturizing the electrodes, but in making such small components durable. Corrosion of metals in surgical implants is a widespread issue, and since metal is both the functional and corrosive part, the metal quantity is crucial.
The implant developed by Asplund and her team is a mere 40 micrometers wide and 10 micrometers thick, with metal parts only a few hundred nanometers thick. To combat corrosion, the team employed a unique blend of materials, including a conducting polymer that transmits the electrical stimulation needed for the implant to function and forms a protective layer over the metal, enhancing the electrode’s corrosion resistance.
This innovative combination of conducting polymer and metal could potentially enable vision implants to function throughout the implant’s lifespan. The next aim is to develop an implant capable of connecting to thousands of electrodes, a task currently being explored within the ongoing EU project Neuraviper.
In a study conducted by the Netherlands Institute for Neuroscience, mice were trained to respond to electrical impulses sent to their brain’s visual cortex. The experiment demonstrated that mice could rapidly learn to react to the electrode-induced stimulation, and that the required current for mice to perceive the stimulation was lower than standard metal-based implants. Moreover, the implant’s functionality remained stable over time, even until the end of a mouse’s natural lifespan in one instance.
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