Structural Evaluation by the Finite‐Element Method of Hollow Microneedle Geometries for Drug Delivery

Abstract

Herein, the structural comparison, using the finite‐element method (FEM), of different designs of individual hollow microneedles (MNs) is exposed, that is, conical, pyramidal, traditional, and sting type, for use as a transdermal drug delivery system (TDDS). These configurations attract interest in fields such as pharmaceutics and medicine due to their efficiency, easy administration of drugs, and significant reduction in pain compared to the traditional use of hypodermic needles. For the structural analysis and comparison of the proposed designs, ANSYS FEM‐based software is used to simulate the insertion of an MN in the skin. The study and comparison are carried out under simulations of structural resistance, buckling analysis, and behavior in the MN–skin contact. The application forces are set according to the fracture resistance of the outside layer of the skin. A force of 0.16N for a conical MN is finally obtained as a critical application load to avoid a structural failure in the insertion of the MN in the human skin. Moreover, the use of poly(lactic‐co‐glycolic) acid (PLGA) is also assessed as a second biocompatible alternative due to both its easy handling for manufacture process and the resistance it presents in indentation simulations in which the applied force reaches 0.19N.

Development of an Automated Design Tool for FEM-Based Characterization of Solid and Hollow Microneedles

“…In Henriquez et al [ 23 ], an FEM analysis is performed considering different geometries and building materials for the MN. The geometries included in the study are: conical, pyramidal, traditional and a proposed sting-bee topology.…”

“… Type of MN Ref. Material Used Material Properties Geometry Dimensions Reported Results Array Size Fabrication Method Application Hollow Out-of-plane [ 23 ] Silicon E = 150 GPa σ y = 165 MPa ν = 0.28 d = 2.33 gcm −3 Conical Pyramidal Beveled Sting type L = 600 μm D b = 300 μm D i = 90 μm (eccentric) For stainless steel conical MN Displacement for skin penetration 0.17 mm Max application force 0.16 N Max lateral force 0.0516N 1 × 1 N/r TDD Stainless steel E = 193 GPa σ y = 207 MPa ν = 0.31 d = 7.75 gcm −3 Polylactic coglycolic acid (PLGA) E = 2.7 GPa σ y = 28.22 MPa ν = 0.25 d = 1.11 gcm −3 Polylactic acid (PLA) E = 1.28 GPa σ y = 53.45 MPa ν = 0.36 d = 1.25 gcm −3 Resin E = 2.2 GPa σ y = 33.7 MPa ν = 0.26 d = 1.16 gcm −3 Solid Out-of-plane [ 39 ] Cycloolefin polymers (COP) …”

“…To the best of the authors’ knowledge, many proposals make use of different CAD software to facilitate geometrical description of their designs [ 10 , 20 , 21 , 23 , 24 ], but none comprises automation of the design process, from selection of modeling and geometrical parameters to analysis of the corresponding FEM simulation results with minimum user interaction.…”

Modeling of Microneedle Arrays in Transdermal Drug Delivery Applications

“…The MNs can be classified according to different criteria, the most widely used being the drug release mechanism, as: solids, coated, dissolvable, hollow, and hydrogels [ 2 , 3 ]. The MNs are design according to a given application, where the geometry is a key parameter and largely defines the functionality in cosmetic, therapeutic, or clinical fields [ 3 , 8 ]. In this way, manufacturing processes can offer characteristic geometries attributable to the manufacturing method as is the case with laser ablation or air-droplet blowing [ 2 , 3 , 4 ].…”

“…Among the types of MNs, hollow MNs stand out, offering an alternative to open a continuous supply channel. However, their hollow and thin characteristics present a challenge at the structural level [ 8 , 10 , 11 , 12 ]. In addition, the behavior of the fluid passing through the system and the composition of the transported drugs must be considered [ 13 ], as this could determine the performance of a specific device [ 10 ].…”