Computational simulation of microneedle penetration in the skin for clinical usage in drug delivery and rejuvenation

Microneedles are a type of micron-sized needles that have been considered in recent years in various fields including drug release and rejuvenation. Simulation of penetration process of the microneedle into the skin is useful for examining the strength of the microneedle and its effect on the skin during penetration. In this study, penetration of the microneedles into the skin was simulated using finite element method. The skin is assumed to be in two layers and the Ogden model is applied to each of them. The path of microneedle penetration into the skin is predicted by cohesive elements. The results show that at a constant velocity of 0.36 mm/s in order for penetrating the epidermis only 0.5 s and penetrating the dermis only 2.5 s is needed. By decreasing the tip diameter of the microneedle, the reaction force applied to the microneedle decreased while the maximum stress in the skin also increased. As a result, it is recommended to use a conical model to design the microneedle. When the microneedle speed increases, the reaction force on the microneedle increases exponentially but these changes are more noticeable at high speeds. This simulation can be useful for medical biopsy sampling, drug release systems as well as stress assessment in rejuvenation.