Design and characterisation of graphene-based nano-photodiode array device for photo-stimulation of subretinal implant

摘要

Electrically stimulating the retina of the patients suffering due to extreme retinal disorders such as age related macula degeneration, retinitis pigmentosa is quickly turning into a feasible accomplishment through retinal implants. The objective of this work is to optimise the design, develop and test an organic photovoltaic based Nano Photo Diode Array (NPDA) device for retinal prosthesis application to restoring vision to patients blinded by degenerative retinal diseases. NPDA for subretinal stimulation has been fabricated based on Bulk heterojunction (BHJ) solar cell technology. Each pixel is composed by a graphene alone bottom anode, a semiconducting single wall carbon nanotube (S-SWCNT):C60 blend, and a top cathode in aluminum (Al) of 100 mu m or 150 diameter. This NPDA device photovoltaically converts incident light into electric current to stimulate nearby retinal neurons without wired power connections. The fabricated device is able to provide a photo current density of 245 mu A/cm(2) and photovoltage of 0.31 V. These results suggest that BHJ cell employed photodiode array used in this work make it better than POLYRETINA and SCNC. The significant improvement in photocurrent density paves the way for scaling up density of NPDA array in implant. Increased number of electrodes will indeed enhance visual acuity to greater extent.