Development and experimental verification of a nonlinear hyperelastic model for microneedle-skin interactions

Over the years, microneedles with varieties of materials and shapes have been fabricated, however, simulation of the penetration of microneedle through the skin are seldom reported. This paper reports on modeling and verification of microneedle-skin interactions. For the first time, a nonlinear hyperelastic model on the micro scale for large deformation is developed to determine several phenomena during the inserting. The accuracy is experimentally verified by measuring the relationship between force and displacements during the insertion of mouse skin. To prove the breakage on the skin, the permeability is tested for diclofenac. The cumulative permeation with pierced skins is 10,000 times larger than untreated counterpart. The simulation results indicated that the maximum insertion force produced when microneedles array was inserted perpendicularly and insertion force increased strongly with the tip width. Based on this model, the design of microneedle can be optimized.