Additive Manufacturing of Honeybee-Inspired Microneedle for Easy Skin Insertion and Difficult Removal.

With natural evolution, honeybee stinger with microbarbs can easily penetrate and trap in the skin of hostile animals to inject venom for self-defense. We proposed a novel three-dimensional additive manufacturing method, namely magnetorheological drawing lithography, to efficiently fabricate a bioinspired microneedle imitating a honeybee stinger. Under the assistance of an external magnetic field, a parent microneedle was directly drawn on the pillar tip, and tilted microbarbs were subsequently formed on the four sides of the parent microneedle. Compared with the barbless microneedle, the microstructured barbs enable the bioinspired microneedle for easy skin insertion and difficult removal. The extraction-penetration force ratio of the bioinspired microneedle was triple that of the barbless microneedle. The stress concentration at the barbs helps to reduce the insertion force of the bioinspired microneedle by minimizing the frictional force, whereas it increases the adhesion force by interlocking the barbs in the tissue during retraction. Such finds may provide an inspiration for further design of barbed microtip-based microneedles for tissue adhesion, transdermal drug delivery, biosignal recording, and so on.