Silicon dioxide microneedles for transdermal drug delivery

In this work, the fabrication of a silicon chip for transdermal drug delivery is reported. The chip consists of: 1) an array of high-aspect ratio (up to 50), high density (1 times 10⁶ needles/cm²), silicon-dioxide hollow microneedles to be inserted into the outermost part of the skin for a depth of about 100 micron (front-side); 2) some independent drug reservoirs (each one with a volume of about 1 microliter) on the back-side, connected to the needles. The needle fabrication was performed by exploiting an electrochemical micromachining (ECM) technology which offers a number of advantages with respect to both traditional dry (RIE, DRIE) and wet (KOH, TMAH) etching processes. The high flexibility, high reliability and, most important, low cost of the ECM technology yield the proposed approach very attractive for the mass production of the chip.