Numerical Simulation of the Process of Inserting Micro-needles into Skin

Micro-needle, as a novel way for transdermal drug delivery, due to its painless and minimally invasive nature, has recently attracted much attention. The research into the mechanism of inserting micro-needles into skin is important not only for an optimum design of the micro-needles, but also for further applications of the micro-needles in the drug delivery. Based on the mechanical properties of different skin layers and the failure criterion of the material, the process of the insertion of micro-needles into a skin is analyzed with nonlinear finite element software Abaqus. The interaction between the micro-needle and skin during the insertion process of the micro-needle is visualized. The deformation and failure of the skin and general behavior of the micro-needle force-displacement history are discussed. The insertion force can be obtained. The influences of the micro-needle geometry (eg. tip area, wall angle, wall thickness) on the insertion force is revealed. Numerical simulations show that the needle tip area and the needle wall angle are the primary control parameters for the process of inserting micro-needles into the multilayer human skin, whereas other factors, such as the wall thickness of the micro- needle, are much less important. A qualitative agreement between the computation and the test results is obtained. This provides a basis for design of a micro-needle drug delivery system in general and of the micro-needles in particular.