Reusable High Aspect Ratio 3-D Nickel Shadow Mask

Shadow mask technology has been used over the years for resistless patterning and to pattern on unconventional surfaces, fragile substrate, and biomaterial. In this paper, we are presenting a novel method to fabricate high aspect ratio (15:1) 3-D nickel (Ni) shadow mask with vertical pattern length and width of 1.2 mm and 40 μm, respectively. The Ni shadow mask is 1.5 mm tall and 100 μm wide at the base. The aspect ratio of the shadow mask is 15. Ni shadow mask is mechanically robust and, hence, easy to handle. It is also reusable and used to pattern the sidewalls of unconventional and complex 3-D geometries, such as microneedles or neural electrodes (such as the Utah array). The standard Utah array has 100 active sites at the tip of the shaft. Using the proposed high aspect ratio Ni shadow mask, the Utah array can accommodate 300 active sites, 200 of which will be along and around the shaft. The robust Ni shadow mask is fabricated using laser patterning and electroplating techniques. The use of Ni 3-D shadow mask will lower the fabrication cost, complexity, and time for patterning out-of-plane structures.