In this paper, we present design, fabrication and coupled multifield analysis of hollow out-of-plane silicon microneedles with piezoelectrically actuated microfluidic device for transdermal drug delivery (TDD) system for treatment of cardiovascular or hemodynamic disorders such as hypertension. The mask layout design and fabrication process of silicon microneedles and reservoir involving deep reactive ion etching (DRIE) is first presented. This 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. Then coupled multifield analysis of a MEMS based piezoelectrically actuated device with integrated silicon microneedles is presented. The coupledfield analysis of hollow silicon microneedle array integrated with piezoelectric micropump has involved structural and fluid field couplings in a sequential structural-fluid analysis on a three-dimensional model of the microfluidic device. The effect of voltage and frequency on silicon membrane deflection and flow rate through the microneedle is investigated in the coupled field analysis using multiple code coupling method. The results of the present study provide valuable benchmark and prediction data to fabricate optimized designs of the silicon hollow microneedle based microfluidic devices for transdermal drug delivery applications.
The origin of p–n junction reverse current is investigated by a method based on the analysis of the leakage current activation energy. Its main advantages lie in the possibility to distinguish multiple reverse-bias dependent leakage components and determine their mechanisms, which can be different than the Shockley–Read–Hall or field-enhanced generation mechanisms. This is illustrated for state-of-the-art silicided shallow junctions, exhibiting a local Schottky effect, due to small-area silicide penetrations. An estimate of the area of the Schottky (or Shannon) contacts follows from the analysis. The method may be used for various semiconductor materials and leakage current origins.
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