Artificial Retina

Artificial Retina


The retina is a  light-sensitive layer of cells in the eye. Light-sensitive neurons in the back of the eye convert light to electric signals, other cells process these nerve impulses and transmit them to the brain. The motivation to achieve wireless access to electrophysiological processes has driven the field of optogenetics, involving genetic transfection of target cells with light‐sensitive ion channels. However, the reliance on genetic modification imposes many obstacles.

Yael Hanein, Tel Aviv University, Israel, and Eric Daniel Glowacki, Linköpings Universitet, Norrkoping, Sweden, and colleagues have developed a nanoscale, simple photoactive film that converts light impulses into electrical signals. The photoactive film consists of an 80 nm trilayer of metal and p–n semiconducting organic nanocrystals. A surrounding physiological electrolyte is in contact with both the bottom metal and the top of the p–n junction. The semiconductor layers have been made using ubiquitous and nontoxic commercial pigments via sequential physical vapor deposition through stencil masks. This allows controlling geometries and compatibility with various substrates.

When illuminated in physiological solution, the metal–semiconductor devices charge up, transducing light pulses into localized displacement currents that are strong enough to electrically stimulate neurons with safe light intensities. The devices are freestanding, requiring no wiring or external bias, and are stable under physiological conditions.

The team demonstrated effective direct photostimulation of light‐insensitive embryonic chicken retinas. Their idea is to use these first non‐Si optoelectronic platform capable of sufficiently large photovoltages and displacement currents to enable true capacitive stimulation of excitable cells to restore sight to blind people.

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