There are many challenges in designing neuroprostheses and one of them is to maintain proper axon selectivity in all situations. This project is based on an electrode that is implanted into a fascicle in a peripheral nerve and used to provide tactile sensory feedback of a prosthetic arm. This fascicle can undergo mechanical deformation during every day motion. This work aims to characterize the effect of fascicle deformation on axon selectivity and recruitment when electrically stimulated using hybrid modeling. The main framework consists of combining finite element modeling (FEM) and simulation environment NEURON. A suite of programs was developed to first populate a fascicle with axons followed by deforming the fascicle and rearranging axons accordingly. A model of the fascicle with an implanted electrode is simulated to find the electrical potential profile through FEM. The potential profile is then used to compare which axons are activated in the two conformations of the fascicle using NERUON.
This analysis explores what the time needed to harden, and time needed to degrade is of a PLGA bead, as well as whether the size of the needle injecting the bead and the addition of a drug (Vismodegib) may affect these variables. Polymer degradation and hardening are critical to understand for the polymer’s use in clinical settings, as these factors help determine the patients’ and healthcare providers’ use of the drug and estimated treatment time. Based on the literature, it is expected that the natural logarithmic polymer mass degradation forms a linear relationship to time. Polymer hardening was tested by taking video recordings of gelatin plates as they are injected with microneedles and performing RGB analysis on the polymer “beads” created. Our results for the polymer degradation experiments showed that the polymer hardened for all solutions and trials within approximately 1 minute, presenting a small amount of time in which the patient would have to remain motionless in the affected area. Both polymer bead size and drug concentration may have had a modest impact on the hardening time experiments, while bead size may affect the time required for the polymer to degrade. Based on the results, the polymer degradation is expected to last multiple weeks, which may allow for the polymer to be used as a long-term drug delivery system in treatment of basal cell carcinoma.