Self-Unfolding Flexible Microelectrode Arrays Based on Shape Memory Polymers

Most of the current concepts for a visual prosthesis are based on neuronal electric stimulation. However, existing visual prostheses confront several challenges in electrodes that limit the effectiveness of stimulation. First, there is an inherent conflict between the needs of minimally invasive implantation for minimizing traumas and the requirements of implanted electrodes with large areas for obtaining wide field and high-resolution vision. Second, the mechanical and geometrical mismatches between implanted electrodes and retina tissues also affect the effectiveness of stimulation. To address these challenges, flexible microelectrode arrays (fMEAs) with expanded areas, high-density electrodes, and unique self-unfolding capabilities are here reported, which will be feasible for minimally invasive implantation and accommodate large strain and geometrical curvature for potentially improving both the visual field and visual acuity. To obtain the flexible nature and programmable self-unfolding property, the fMEAs are formulated based on a shape memory polymer with appropriate physicochemical properties. At the physiological temperature (37 degrees C), programmable shape deformation from a tubular shape to a unfolded film shape is enabled by the fMEAs with a large area (10 x 10 mm(2)) and high-density electrodes (126 channels), implying their superior potential for minimally invasive implantation, excellent shape adaption to retinal tissues, and high-efficiency stimulation.