Fabrication of Semi-Invasive Micro-Needle Array Using Gradation Exposure

The authors have been investigating a methodology to fabricate a micro-needle array on a thin plastic film for clinical use. The lithography-based approach can be used to produce micro-needle arrays. The purpose of this research is to demonstrate a methodology for etching silicon to particular required depths which can be used in designing structures to manufacture a mold for polymers. A grey-scale photolithography technique was demonstrated using deep reactive ion etching (DRIE). The whole photo-lithography process was carried out in two steps: (i) a photoresist pattern was transferred into silicon dioxide using a layout mask, (ii) a silicon mold was formed using exposure through the use of gradation mask and DRIE. The etch selectivity to the resist was 8.1 and the maximum relative depth was 30 μm.