Mechanical Properties and Fabrication of Bioinspired Cactus Spine Microneedles

Microneedle-based transdermal drug delivery enables painless and efficient drug administration but is limited by insufficient mechanical strength and high insertion forces. Inspired by the efficient penetration capability of cactus spines, this study investigated the microstructure and biomechanics of natural cactus spines and bioinspired microneedles. Finite element analysis showed that a groove width of 50 μm produced the highest stress and strain. Solid bioinspired microneedles were fabricated by 3D printing, while dissolvable hyaluronic acid, chitosan, and gelatin microneedles were prepared using femtosecond laser-fabricated titanium molds and replica molding. Optimized laser parameters generated micropores approximately 500 μm deep. Mechanical tests showed insertion forces of 60-100 mN for solid microneedles, with the 50 μm groove design exhibiting the highest value. Among dissolvable microneedles, gelatin displayed the greatest mechanical strength, whereas hyaluronic acid demonstrated the best overall potential for transdermal drug delivery.