07/08/2016
Engineering a Flexible Organic Photovoltaic Cell as an Artificial Retina to Restore Sight: A Promising Vision in Bio-nanoelectronics
Rachel Rosenzweig, Elena Iris Liang, Mary Nora Dickson and Emma Mah from the University of California, Irvine
Worldwide, over 285 million people are blind and vision impaired; 90% live in low-income settings. Retinal degeneration, including retinitis pigmentosa, age-related macular degeneration, and diabetic retinopathy, affect 100 thousand, 11 million, and 4.4 million Americans respectively. With no known cure for retinal blindness, the only therapy is an artificial retina; however, no developmental device has been completely successful. We aim to use a convergence research approach, integrating materials science, biomedical technology, and life sciences, to engineer an artificial retina composed of soft photosensitive nanomaterials coupled with living neuronal tissues. We are inspired by photovoltaic solar panels, which convert sunlight (photons) into electricity through generating electron-hole pairs due to optoelectronic properties. Our device will act as a miniature, flexible, biocompatible, organic solar panel. Upon light stimulation, our device generates voltage signals with high spatial resolution that will alter the membrane potentials of overlying neurons, sending action potentials to activate the visual system. Our artificial retina provides a promising vision in bio-nanoelectronics, encompassing biology, nanotechnology, and electronics.
Our proposed idea will provide a cost-efficient, mechanically robust, long-term solution to patients suffering from retinal degeneration. Our device must meet these design criteria: mechanical durability, flexibility to prevent tissue damage, compatibility with the nervous system, adequate charge generation properties, and high resolution (600-1000 localized voltage sources required for face recognition and reading large text). To meet these requirements, we will design an organic photovoltaic cell that uses an inexpensive, biocompatible, polymer-based material to convert light into pulsed electric signals, stimulating nearby neurons for visual processing through optical excitation. Using nanofabrication techniques, we can fabricate an array of over 10000 such cells, thereby exceeding the resolution requirement.
Previously, others have explored inorganic microelectronics and silicon-based microphotodiode arrays to serve in artificial retinas. Limitations with such devices are rigidity, propensity to elicit chemical reactions, dissolvability, dependence on external co-devices, and electrical inefficiency. Our use of an inherently flexible, biocompatible, and electroactive polymer is designed to eliminate these problems without sacrificing light sensitivity over the full spectrum of visible light. Our team has broad experience in the medical applications of polymer nanoimprint lithography, a cost-efficient, industrial process for making the sensing elements. We harness this for the retina device to rationally design nanoarchitectures that will both allow for the desired pixel resolution and enhance the performance of organic photovoltaics with improved charge transport properties. Our first application of polymer nanostructures to advanced medical devices is published in BioInterphases along with pending patents co-first authored and invented by two of our team’s members. The grand vision of our multidisciplinary approach is to engineer an affordable, long-lasting, biocompatible, self-contained, high resolution, and electrically efficient bio-nanoelectronic device as an artificial retina to restore native vision in patients around the world.
Image credit for this goes to: Rachel Rosenzweig, Elena Liang, and Mary Dickson
