Finite element analysis of hollow out-of-plane HfO microneedles for transdermal drug delivery applications.

Transdermal drug delivery (TDD) based on microneedles is an excellent approach due to its advantages of both traditional transdermal patch and hypodermic syringes. In this paper, the fabrication method of hollow out-of-layer hafnium oxide (HfO) microneedles mainly based on deep reactive ion etching of silicon and atomic layer deposition of HfO is described, and the finite element analysis of the microneedles based on ANSYS software is also presented. The fabrication process is simplified by using a single mask. The finite element analysis of a single microneedle shows that the flexibility of the microneedles can be easily adjusted for various applications. The finite element analysis of a 3 × 3 HfO microneedle array applied on the skin well explains the "bed of nail" effect, i.e., the skin is not liable to be pierced when the density of microneedles in array increases. The presented research work here provides useful information for design optimization of HfO microneedles used for TDD applications.