Design, Fabrication and Analysis of Silicon Microneedles for Transdermal Drug Delivery Applications

One of the major drawbacks of transdermal drug delivery (TDD) systems has been their inability to deliver the drugs through the skin at therapeutically desirable range. To overcome this limitation, use of microneedles is gaining popularity. In this paper, the use of microneedles has been proposed for the transdermal drug delivery applications. By using the processes developed by microelectronics industry, the hollow cylindrical silicon microneedles array has been fabricated with microneedles having the tapered tip for easy skin insertion. Mask layout design and fabrication steps involving deep reactive ion etching (DRIE) using silicon wafers is first presented. The process is followed by actual fabrication of silicon hollow microneedles by a series of combined isotropic and anisotropic etching processes using inductively coupled plasma (ICP) etching technology. The performance of the microneedles is numerically characterized by using structural and coupled multifield analysis. To predict the stress distribution and model fluid flow in coupled multifield analysis, finite element (FE) and computational fluid dynamic (CFD) analysis using ANSYS has been used. Flow rate through the microneedles is investigated at different voltages and frequencies using multiple codes coupling method. The analysis of the flow behavior by coupled field method and structural characteristics provides useful data to fabricate optimized design of the hollow silicon microneedle based drug delivery device for transdermal drug delivery applications.