Micro-3D printing of bio-inspired microneedle with enhanced adhesion capabilities

Microneedles (MNs) are an array of micron-sized needles that have been used as an excellent alternative to invasive and painful hypodermic needles. Due to their micro-scale structure, MNs can overcome the skin barrier without causing significant pain to the patient. Micro-Electro-Mechanical system (MEMS) fabrication techniques have led to the promising applications of MNs in biomedical field such as drug delivery and transdermal bio sensing. However, current fabrication techniques for MNs are complicated and time consuming. Another challenge is to achieve significant tissue adhesion over long periods. Inspired by porcupine quill and honeybee stinger where intricate side profiles promote adhesion to the skin tissue, here we present a micro 3D printed bio-inspired microneedle with backward-facing curved fins. With this side-profile on the MN, the adhesion force is significantly enhanced due to mechanical interlocking of the fins to the skin tissue. To create backward-facing fins on the side of microneedle, we utilize photo-crosslinking density gradient of the polymer to induce curvature in the fins that are horizontally attached to MNs. When such a microneedle is inserted into the skin, the curved fins extruded from the microneedle surface create mechanical interlocking with the skin tissues, resulting in enhanced adhesion of the needles. Geometrical parameters of fins including number of fins, pitch and length is studied to determine optimal configuration to maximize the adhesion performance of the microneedle. Piercing/pull-out test showed adhesion force of single MN per unit area of 2.66 ± 0.33 N/cm2 showing ~20 times higher adhesion force to the tissue compared to microneedles without fins. This unique design of bio-inspired microneedle with enhanced adhesion capability has potential to be used for various transdermal applications such as transdermal drug delivery and transdermal bio-sensing.M.S.Includes bibliographical referencesby Riddish Sudhir Mord