Title : Multiphysics/Multiscale Modeling and Simulation of Organic Retinal Prostheses
In this talk we propose a model for the simulation of retinal prostheses based on the use of organic polymer nanoparticles (NP). The model consists of a nonlinearly coupled system of partial differential equations accounting for: (1) light photoconversion into free charge carriers in the NP bulk; (2) charge transport in the NP bulk due to drift and diffusion forces; (3) net charge recombination in the NP bulk due to the balance between light absorption and particle-particle recombination; (4) electron-driven molecular oxygen reduction and capacitive coupling at the NP-solution interface; (5) ion electrodiffusion in the solution bulk; (6) capacitive and conductive coupling across the neuronal membrane. The proposed model is solved in stationary conditions and in one spatial dimension. System coupling is dealt with a modification of the Gummel Decoupled algorithm conventionally used in inorganic semiconductor simulation. System discretization is conducted using the Finite Element Method, with stabilization terms to prevent spurious unphysical oscillations in the electric potential and ensure positivity of carrier and ion concentrations. Model predictions suggest that the combined effect of NP polarization and resistivity of the NP-neuron interface results in neuron depolarization and supports the efficacy of organic NPs in retinal prosthesis development.