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Adv Mater. 2018 Jun;30(25):e1707292. doi: 10.1002/adma.201707292. Epub 2018 May 2.

Direct Electrical Neurostimulation with Organic Pigment Photocapacitors.

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Tel Aviv University Center for Nanoscience and Nanotechnology, and School of Electrical Engineering, Tel Aviv University, 55 Haim Levanon St., Tel Aviv, 699780, Israel.
Laboratory of Organic Electronics, Department of Science and Technology, Linköpings Universitet, Bredgatan 33, 60174, Norrköping, Sweden.
Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, POB 12, Rehovot, 76100, Israel.
Center of Excellence for Advanced Materials and Sensing Devices, Ruđer Bošković Institute, Bijenicˇka cesta 54, 10000, Zagreb, Croatia.
Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, I-40127, Bologna, Italy.
Linz Institute for Organic Solar Cells (LIOS), Johannes Kepler University, Altenbergerstrasse 69, A-4040, Linz, Austria.


An efficient nanoscale semiconducting optoelectronic system is reported, which is optimized for neuronal stimulation: the organic electrolytic photocapacitor. The devices comprise a thin (80 nm) trilayer of metal and p-n semiconducting organic nanocrystals. When illuminated in physiological solution, these 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 in physiological conditions. The semiconductor layers are made using ubiquitous and nontoxic commercial pigments via simple and scalable deposition techniques. It is described how, in physiological media, photovoltage and charging behavior depend on device geometry. To test cell viability and capability of neural stimulation, photostimulation of primary neurons cultured for three weeks on photocapacitor films is shown. Finally, the efficacy of the device is demonstrated by achieving direct optoelectronic stimulation of light-insensitive retinas, proving the potential of this device platform for retinal implant technologies and for stimulation of electrogenic tissues in general. These results substantiate the conclusion that these devices are the first non-Si optoelectronic platform capable of sufficiently large photovoltages and displacement currents to enable true capacitive stimulation of excitable cells.


artificial retina; bioelectronics; neurostimulation; organic semiconductors


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