Development of a Microfluidic Drug Delivery Neural Stimulating Device for Vision

Abstract

Abstract: : Purpose: We have developed a microfluidic retinal prosthesis, using wide bandgap semiconductor thin film waveguides and microfluidic delivery arrays to facilitate spatial and quantitative photoactivation of caged neurotransmitter. Methods: Novel waveguide materials, micromachining technology, and computational fluid dynamics (CFD) simulations are necessary to fabricate 360nm capable waveguides and fluid delivery arrays for the microfluidic device. Single crystal AlN wide bandgap semiconductor thin films are grown on sapphire with high refractive index buffer layer by plasma source molecular beam epitaxy (PSMBE). 248 nanometer KrF Excimer laser micromachining technology is employed to micro-fabricate wave-guiding channels and microfluidic structures. CFD software is used in the simulation of fluid flow through the microfluidic arrays. Results: A low density waveguide and fluid array as well as a high density AlN/Sapphire waveguide and corresponding fluid array which allow for spatial and temporal drug delivery within the retina were fabricated. Wave-guiding channels were precisely fabricated to form a cavity to maximize the intensity of ultraviolet light. Wave-guiding properties were efficiently characterized as a function of thickness, geometry and crystalline quality. Fluid dynamics through our devices were analyzed using CFD software. Conclusions: There is a need for a neural prosthesis that may be used in physiological drug delivery systems. A device that may deliver UV light and "caged" neurotransmitters in precise amounts and to selective areas of a microfluidic implant without direct ultraviolet exposure to the biological cells is much needed in retinal and cortical implants. Results of the design and fabrication of a high and low density microfluidic chip and waveguide system will be presented.

Keywords: retina • neurotransmitters/neurotransmitter systems