Ocular diseases such as glaucoma, age-related macular degeneration (AMD), diabetic retinopathy, and retinitis pigmentosa require drug management in order to prevent blindness and affecting millions of adults in US and worldwide. There is an increasing need to develop devices for drug delivery to address ocular diseases. This research focused on an implantable ocular drug delivery device design, simulation and experiments with design requirements including constant diffusion rate, extended period of time operation, the smallest possible volume of device and reservoir. The drug delivery device concept uses micro-/nano-channels module embedded between top and bottom covers with a drug reservoir. Several microchannel design configurations were developed and simulated using commercial finite element software (ANSYS and COMSOL), with a goal to investigate how the microchannel dimensions affect the diffusion characteristics. In addition to design simulations, various microchannel configurations were fabricated on silicon wafer using photolithography techniques as well as 3D printing. Also, the top and bottom covers of the device were fabricated from PDMS through replica molding techniques. These fabricated microchannel design configurations along with top and bottom covers were all integrated into the device. Both single straight microchannels (nine different sizes of width and depth) as well as four micro-channel configurations were tested using citric acid (pH changes) and Brimonidine drug (concentration changes using the Ultra-Violet Visible Spectrophotometer) for their diffusion characteristics. Experiments were conducted to obtain the diffusion rates through various single micro-channels as well as micro-channel configurations using the change in pH neutral solution to verify the functionality and normalized diffusion rate of microchannels and configurations. The results of experimental data of diffusion rate were compared with those obtained from simulations, and a good agreement was found. The results showed the diffusion rate and the optimum size of microchannel in conjunction with the required drug release time. The results obtained also indicate that even though specific diffusion rates can be obtained but delivering the drug with constant amount needs a mechanism at the device outlet with some control mechanism. For future studies, this result may be used as a baseline for developing a microfabricated device that allows for accurate drug diffusion in many drug delivery applications.

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