A method to predict insertion of dissolvable microneedles: No need to fabricate

This paper investigates the insertion of dissolvable microneedles into skin, which is a challenging topic in the design and application of dissolvable microneedles. Traditionally, this phenomenon has been evaluated through mechanical tests and experimental studies. To address this issue, this paper presents mathematical equations for predicting the insertion of pyramid shape dissolvable microneedles into skin by comparing the failure (buckling) force, which causes microneedle deformation, with the insertion force required for penetration. These equations enable the prediction of microneedle insertion into skin without necessitating microneedle fabrication. The derivation of these equations employed both analytical studies and numerical simulations using ABAQUS software based on the Finite Element Method (FEM). To validate the proposed equations, experimental investigations were also performed on microneedle insertions; obtained results were aligned closely with outcomes predicted by the equations. The results indicate that the insertion of dissolvable microneedles into skin is influenced by the geometry and the mechanical properties of the microneedle. Additionally, a key finding of this study is that the effects of additives and active pharmaceutical ingredients (APIs) must be considered when assessing the insertion of dissolvable microneedles into skin. Additionally, the findings have been distilled into general statements that encapsulate the core principles, offering practical recommendations and design considerations for researchers to enhance the likelihood of successful microneedle insertion. To further assist researchers in utilizing the presented equations, a proposed protocol is provided, serving as a roadmap for effectively applying the information presented.