3-d Patterned Microstructures Using Inclined Uv Exposure and Metal Transfer Micromolding

We report a fabrication approach for three-dimensional (3-D) microstructures having functional metal patterns by using inclined UV lithography and 3-D metal transfer micromolding. Inclined rotational UV exposure using SU-8 has been exploited to simultaneously generate gradually varying 3-D structures with different heights in a single mask. For 3-D metal patterning, a metal transfer micromolding process has been utilized, where prepatterned metal electrodes are formed on a polydimethylsiloxane (PDMS) mold prior to transfer, and these patterned metal structures are transferred to the molded 3-D microstructures during the micromolding process. Two approaches for metal prepatterning have been utilized: one is selective metal removal by planar pattern transfer on an uneven surface and the other is pattern transfer using a shadow mask. Two test vehicles of 3-D patterned microstructures implemented by this process are demonstrated: an electroporation microneedle array and a 3-D microelectode array (MEA). Insertion tests on pig skin using the fabricated microneedle array with different heights have been successfully performed, showing different penetration depths by fluorescent imaging.