Ultra-high responsivity, silicon nanowire photodetectors for retinal prosthesis

In this paper, a novel silicon nanowire photodetector on a flexible substrate is presented for replacing the function of photoreceptors in the retina to restore vision for the blind. An extremely high surface-to-volume-ratio characteristic of nanowire is capable of developing highly-sensitive photonic sensors. Therefore, a nanowire photodetector can be used as a stand-alone visual perception device without an external camera. The nanowire photodetector is first fabricated on a rigid substrate, and then transferred to a flexible substrate to fit the curvature of an eyeball. Experimental results using the fabricated silicon nanowire photodetector show very high photosensitivity and photoresponsivity for a wide range of light intensities and wavelengths. Mechanical bending tests are performed, and the results show that the optical performance of the flexible photodetector is well-preserved after repeated bending of 200 times. The presented performance evaluation results indicate the first viable alternative to using a camera for image acquisition.