Finite Element Analysis of Skin Deformation and Puncture for Microneedle Array Design.

The mechanics of microneedle insertion have thus far been studied in a limited manner. Previous work has focused on buckling and failure of microneedle devices, while providing little insight into skin deformation, puncture, and the final positioning of needle tips under full microneedle arrays. The current study aims to develop a numerical approach capable of evaluating deformation and puncture conditions for full microneedle array designs. The analysis included a series of finite element submodels used to calibrate the microneedle-epidermal interface for failure properties using traction-separation laws. The single needle model is validated using experimental data and imaging, including results from a customized nanoindentation procedure to measure loads and displacements during microneedle insertion. Upon validation, full microneedle arrays are implemented in a 3 D finite element model and a design framework is developed, allowing evaluation of different design variables (i.e. needle shape, material, spacing) with respect to outputs relevant to successful microneedle performance. Results from the model include skin deformation, force to puncture, penetration depth, and the punctured state at each microneedle tip. In addition to microneedle parameters, patient parameters such as subcutaneous tissue thickness are included to evaluate the sensitivity of different microneedle designs to expected patient and anatomical region variability.