The Theoretical And Experimental Study Of Microneedle Array Inserting Into Skin

Microneedle arrays, as a novel technology, have received increasing attention. Because the Microneedles are very small, they can be widely used for transdermal drug delivery and biochemical sampling in a painless and minimally invasive manner with high efficiency. However, microneedles are also easily failed by fracture and bulking during inserting into skin due to their micro-scale. These mechanical problems strongly hinder the applications of microneedles in clinical therapies. Unfortunately, only a few efforts have been made to overcome such mechanical problems during inserting into skin.In this thesis, we study the penetration behaviors of the microneedles and microneedle arrays by means of experiments and numerical simulations. The finite element model can investigate the effect of the multi-layer structure of the skin on the insertion behave. Moreover, by writing a VUMAT subroutine, the finite element model can simulate the hyperelastic of the skin and the failure process of the skin. Taking advantages of this model, the influences of the microneedle geometry (microneedle angle, tip curvature) on the insertion force is revealed. It was found that an optimization needle angle and tip curvature can be obtained by detailed numerical analyses. These optimized microneedles can insert into the skin with a minimal force, but also can avoid mechanical failure like buckling or fracture. Finally, this thesis study the influence of the microneedle distribution on the insertion force of the microneedle array by numerical analysis and experiment. It was found that the insertion force into the skin (silica gel) can be decreased by increasing the microneedle space of microneedle array. These results can be utilized for optimizing the microneedle array.