Fluid Analysis of Polymer Microneedle for Transdermal Drug Delivery

Microneedle is a device that is used to transport the drugs into human skin. The drug is delivered into the multilayered skin layers consisting of epidermis, dermis, and stratum corneum. During the insertion process, the failure of the microneedle mainly takes place due to the bending and buckling behavior. The failure of the microneedle may lead to the entry of foreign particles inside the human body which would create a serious problem.  So, the selection of materials, geometrical properties, and structural design has to taken care of.  In this paper, the classification of microneedle based on the fabrication, types, geometrical shape, drug delivery approach, and material used is discussed. Based on the fabrication process the microneedle is classified as a) in-plane microneedle and b) out of plane microneedle. The In-plane microneedle is positioned parallel to the substrate surface and out of plane microneedle, the needles protrude out of the surface. Based on the types, microneedles are classified into solid microneedle, coated microneedle, hollow microneedle, and dissolving microneedle. Solid microneedles are constructed as a whole solid structure. The coated microneedle is achieved by coating the solid microneedles with water-soluble drugs. Hollow microneedles are designed to infuse milliliter quantities of fluid into the skin to make transdermal delivery of many drugs possible and to provide a minimally invasive alternative to conventional hypodermic needles. Dissolving microneedles are self-dissolvable and are fabricated using biodegradable materials. Based on the geometrical shape, the microneedle shapes so far designed include cylindrical, conical, tapered, and pyramidal-shaped microneedles. Based on drug delivery the microneedles are classified into i) poke with patch approach, ii) coat and poke approach, iii)poke and flow and iv) poke and release approach. Based on the materials, microneedles are fabricated using silicon, metal, glass, composite, and polymer. Considering various materials, polycarbonate (PC) a biocompatible polymer material is chosen for microneedle design. Microneedles are available in plenty of shapes, sizes, and materials. Designing appropriate microneedle involves a challenging process. The insertion of microneedle into human skin without pain and needle fracture leads to a suitable design. Also, the fluid-structure interaction during the drug delivery process will have a minimum effect on the microneedle structure and fluid flow rate. Hence the fluid analysis is performed using ABAQUS software to simulate the fluid-structure interaction. The fluid flow rate for various drugs considered during the simulation is compared with the conventional silicon microneedle. Therefore the optimal fluid flow rate is identified for safe drug delivery.