فهرست مطالب یاسمن امیری

The study of axonal behavior under different environmental conditions can provide a better insight into the development of therapeutic approaches for healing after nerve damages. By modeling of sublayer in the form of a hyperelastic material and applying different pressures, the amount of strains tolerated by the axon was calculated. Strains were applied at three different time intervals to examine the effects of different strain rates. For axon, a model containing microtubules with linear elastic properties, neurofilament, and axolemma with linear viscoelastic properties was considered. The finite element method and COMSOL software were used for the discretization of the sublayer and the substructures of the axon. It was observed that the fluid regime in the channel did not affect the mechanical response of the axon. The strain was close to zero (at most 0.0001) and the stress was also negligible (at most, 70 N/m2). The results showed the major effect of microtubules on resisting mechanical forces and on the overall integrity of the axons. Most of the strains were seen inside the axolemma, indicating the importance of its mechanical response to injury. Regarding the response to the strain rate, the most probable damage to the axon, comparable with the former corresponding reports will occur at the strain of 42% and strain rate of 19.1 s-1, respectively.

Microneedles are a type of micron-sized needle that is the third most widely used delivery system after oral and injectable drug delivery, used in a variety of fields including drug release and rejuvenation. Optimizing the geometry of microneedles to reduce pain and inflammation has been important in recent years. Due to the high cost of microneedle fabrication, numerical simulation of microneedle penetration into the skin can be useful to evaluate the microneedle strength as well as its effect on the skin during penetration. In this study, first a new simulation method in Abaqus software with explicit method using cohesive elements to investigate the penetration of microneedles in the skin of the human forearm was presented. The skin was considered as Ogden and bilayer hyperelastic models. The microneedle was considered as a rigid body and a constant velocity of 0.6 mm/s was applied to it .The microneedle with bulk with bio-inspired titles was examined and its important parameters such as height, sharpness and bulk angle were evaluated. Finally, some proposed models of microneedles with longitudinal grooves are presented to increase the concentration of stress on the skin and prevent friction. A comparison of the designed microneedle with the barbless microneedle shows that the barbed microneedle concentrates more than twice as much stress on the skin, but reduces the penetration force by as much as 15%, making it easier to penetrate the skin. The results show that the reduction longitudinal grooves increase the tension created in the skin by about 10%, but have little effect on the penetrating force on the skin.